Perhaps the most remarkable thing about the Christian God is his desire to have a relationship with his human creatures. He wants to talk to us and wants us to talk to him, and we call this prayer.
God saves his human creatures because he wants children. This means prayer is, fundamentally, our relational connection with him. And this communication is in many ways more powerful than our communication with each other, because while communication between two humans is by its nature colored with distortion and misunderstanding, God understands us completely because by his Holy Spirit he is in our mind and heart. And the point of this intimate communication is not primarily to learn new things, but so God can spend time with us.