The main purpose of Prayer is simply to bring the Will of God into this earth. Faith and prayer are the mechanics behind bringing God’s will into this World.
And it came to pass, that, as he was praying in a certain place, when he ceased, one of his disciples said unto him, Lord, teach us to pray, as John also taught his disciples. (2) And he said unto them, “When ye pray, say, Our Father which art in heaven, Hallowed be thy name. Thy kingdom come, Thy will be done, as in heaven, so in earth. (3) Give us day by day our daily bread. (4) And forgive us our sins; for we also forgive every one that is indebted to us. And lead us not into temptation; but deliver us from evil.” Luke 11:1 – 4
The end result of prayer is to glorify God in the earth. God is glorified by having his will manifested through prayer.