Christians, how do you define the power of prayer?

Well my friend Prayer is based on two things, the power of faith and the power of God. With the faith of a mustard seed, one can move mountains. God also says that if we ask it then we shall receive. It also depends on if it is God's will or not. I am going to take your example for my example. If you ask God to take that mountain and cast it into the sea, it is probably just a prayer asking God to prove himself, and God doesn't like that. So in the end a prayer is only as strong as the person's faith who is praying, and if it is the will of God. Hope I helped =), God Bless