Greetings to you, Nadya.
The prayer "Our Father Who art in heaven", along with prayer in Jesus' name, is given to us by the Lord Jesus Christ Himself. That is why it is often called the Lord's prayer. The Church's Holy Fathers used to call it a mini Gospel. It is helpful to read their interpretation of this prayer which is great in power and meaning. It is given in two versions in the Gospels according to Matthew and Luke. The Church has accepted Saint Matthew's version. For a better understanding of this prayer, let me quote it in a broader context.
7 And in praying use not vain repetitions, as the Gentiles do: for they think that they shall be heard for their much speaking.
8 Be not therefore like unto them: for your Father knoweth what things ye have need of, before ye ask him.
9 After this manner therefore pray ye. Our Father who art in heaven, Hallowed be thy name.
10 Thy kingdom come. Thy will be done, as in heaven, so on earth.
11 Give us this day our daily bread.
12 And forgive us our debts, as we also have forgiven our debtors.
13 And bring us not into temptation, but deliver us from the evil one.
14 For if ye forgive men their trespasses, your heavenly Father will also forgive you.
15 But if ye forgive not men their trespasses, neither will your Father forgive your trespasses.
As we see, the main worth of this prayer (let alone its origination) is in its economy of words and in absence of all that is redundant. Praying according to it is founded upon a profound faith in God as one's loving and caring Father. Before the coming of Jesus Christ, no one had dared to consider God as his Father, but as Lord (i.e. Master). By becoming a human, Jesus Christ, being by nature the Son of God, has made us sons of God by grace, as His own brethren. But faith in the Father (moreover, in the Almighty One) implies His foreknowledge of our needs prior to our asking and even before our birth. That is why it is obligatory to exclude any petitions for petty and earthly things in order not to become like pagans in this. We ought to understand that our petitions in this prayer are not about informing God of our needs but about a heartily unification with our Heavenly Father with revealing of our hearts' desires before Him as a testimony to the fact that we do actually realize our need in what we ask for, that we are sincere in our desire to receive it, that we hope to receive it only from God and only by His mercy. With this, we declare our part in receiving forgiveness of our sins which is in the keeping of the condition of this forgiveness our forgiving of our neighbors' sins committed against us. Sins in this prayer are called "debt" and sinners "debtors".
Well, let's begin considering this prayer line by line:
Our Father who art in heaven, It's an address to God by confessing Him as one's Father and by pointing out our understanding (and reverence linked to it) of the fact that He, compared to us, is in an unapproachable light and unconceivable glory, which is expressed by saying "Who art in heaven". Here, heaven is not the sky visible to us but the spiritual dimension of God's limitless omnipresence which in no way is connected to or dependent on creatures.
Hallowed be thy name. We cannot do without the name of God! God reveals Himself to us in His name and with His name which is blessed forever and ever! The nature itself of assigning names is of God. Everything is blessed and sanctified (hallowed, set apart) by the name of God, for it is the source of holiness and of blessing. At the name of God (namely, at the name of Jesus Christ the Son of God) bows every knee of those in heaven, and of those on earth, and of those under the earth. The holiness of an intelligent and eternal creature (angel or man) is the highest possible concentration of God's grace in such creature. For example, the name of the reverend Seraphim of Sarov brings us instantly to that specific wonderful man and God-pleaser who was equal to the seraphim. And if his name and the names of other saints to whom the grace of God was imparted as to His creatures, are so honored in heaven and upon the earth, then how much more should be hallowed the name of the natural source of all holiness and grace of the Lord God!? It's by these words that we express this incomparable superiority and lordship of God's name in the creation.
Thy kingdom come. This is our first petition. What is it about? About the coming of the fullness of the grace of God or of the Holy Spirit, the Life-giving Lord called the Kingdom of God. God by nature is holy and most holy but I am far from this holiness. How can I receive it? Only by the coming to me or to us (the children of the Church) of the Holy Spirit Who purifies us and unites us with God by enthroning Him in our hearts. Where the Kingdom of God is, there God is! God is King in the spiritual realm, but He is not in us who are fallen and slid back. That's why we ask Him to give us back His Kingdom, the Kingdom of peace, love, grace and joy in the Holy Spirit.
Thy will be done, as in heaven, so on earth. What is it that hinders the coming of the Holy Spirit to us and His abiding in us? It is our free will at war with the will of God. If the high-handedness of the subjects does not willfully obey the will of their King, then there can't be any Kingdom, let alone the one founded on peace and love. We realize this great calamity of ours, a heavy infirmity and a big hindrance to unification with Lord God (i.e. headstrongness, the fallen and carnal will which is resisting God's will) and that's why we ask to fix this the way that on the earth of our hearts, of all of our human being and finally, upon the Earth itself God's will be done, as it is in the spiritual realm. By setting our will in accordance with God's will and by willfully denying our will in His will's favor, we abolish this obstacle and give way to the coming of the Holy Spirit to us.
There is no way we can do this without God's help. This is what we ask for in these short words!
Give us this day our daily bread. Here is another important and necessary petition to us and, along with that, a confession. We confess that we are but short-term pilgrims on this earth and do not know what the coming day will bring along. That's why we live as if for one day's sake believing in the Lord's commandment not to worry about tomorrow. What do we mean by daily bread? In the Church's application, it is the Mystery of the Eucharist during which we partake of the heavenly Bread the Body of Christ by which we are united into one Church as His spiritual and physical Body. This food is necessary for maintaining life in us. The Lord warned us that whoever will not partake of His body and blood, will not have life in him. It turns out then, that in our petition we ask for everything related to the Liturgy: a priest, a temple, everything needed for performing the Mystery and fore mostly, for the descending of the Holy Spirit upon the bread and the wine of the offering, for their transformation into the true body and blood of Christ. It is on purpose that the Church decreed to sing the prayer "Our Father" during the Liturgy prior to the intinction.
The word of God is our bread, too for, according to the word of the Lord, man shall not live by bread alone but by every word proceeding from the mouth of God. Prophets, apostles, evangelists and others preaching on behalf of God in the grace of the Holy Spirit and by the will of God, are called the mouth of God.
On a personal level, every man has his own bread, according to his spiritual need and condition. Since we are all sinners and are in need of repentance, the main bread of repentance for us are weeping and tears.
This is what kind of a daily bread for us sinners each one of us asks for with these words.
And forgive us our debts, as we also have forgiven our debtors. With these words we ask for forgiveness of our sins but, accepting God's commandment and the spiritual law, we combine this petition with God's condition that we have fulfilled before the petition we have wholeheartedly forgiven and forgive always and constantly (as a way of our life in not judging and in active love for our neighbors) all of our offenders and those who cause us trouble, forgive all of their sins they have committed against us.
And bring us not into temptation, Besides positive petitions, we add two negative ones which we ask to deliver us from. The first one is a request to deliver us from evil temptation. What kind of temptation is it? It is not a test which God allows by measure and according to our strength for our spiritual welfare. We won't escape such temptations and they are necessary, helpful and bring about salvation, although they are oftentimes allowed by God to come from demons and evil men. God Himself tempts no one (James 1:13), He never seduces anyone to sin, to commit a crime, but allows or brings a man into temptation by His admission (by withdrawing His protection, help and by admitting the unclean spirits). Since nothing in the world is done without God's will, it is said sometimes that God Himself sends temptations or tempts. But here in this petition, we don't ask to deliver us from various temptations, but namely, not to bring us (each one of us) into a specific temptation the one that surpasses our strength and abilities and leads to falling away from God and to loosing salvation. But temptation (test) of our faith is altogether possible as, for example, the test of Abraham's faith (sacrificing Isaac unto God). By asking God not to bring him into temptation, a Christian does not necessarily resist temptations but humbly confesses his extreme weakness and asks not to bring about a temptation which surpasses his strength. Along with this, he asks God to strengthen his spirit so that he would overcome the temptation and not to be overcome with it. Thus, in other words, we ask to have the strength to go through the inevitable temptation and not to give in and not to be cast down or overcome by it, i.e. to preserve our faithfulness to God in any temptation.
but deliver us from the evil one. This is the last petition in the prayer and the second one among the negatives. The phrase "from the evil one" should be understood as from any evil, both spiritual and bodily, especially from sin as the greatest of evils and the root of all evils and, since devil, the evil spirit, is the author of all evil, we ask to deliver us from the devil and from his demons. But why doesn't it say, "from the evil spirit, the devil, Satan, the unclean spirit, etc", but says "from the evil one"? It's because we ask not only to deliver us from the external source of evil called by those kind of terms, but firstly from our own inner evil spirit which makes us kin to the evil demons. If an evil spirit succeeds at overruling in a man, then he definitively perishes. A demon does not always abide in a man, especially when it refers to a godly Christian and a faithful child of the Church. We won't be able to get rid of demons and their wiles either in this life nor in our wanderings in the air after we die. That's why asking for total deliverance from them is absurd and unrealistic. But it's extremely necessary for our salvation to get rid of our own evil spirit. How is it that our evil spirit is revealed? It's in our complexity (as opposed to simplicity, childishness), hypocrisy and sinful disingenuity, and what is the worst of all, in cunning self-justifications. It's from self-justifications, proceeding from pride, that we firstly ask God to deliver us. There is no way we can be saved having them! That's why the Lord's commandment, "But let your 'Yes' be 'Yes,' and your 'No,' 'No.' For whatever is more than these is from the evil one" is directed to overcome the evil self-justifications which decisively and definitely destroy the man.
Verses 14-15 confirm and affirm the spiritual law which speaks of the necessity of forgiveness of our neighbors' sins against us in order to receive from God the forgiveness of our sins. Transgressors of this law do not receive forgiveness of their sins no matter how hard they try or whatever they do.