Prayer is sent to outside forces.
The benefits are attributed to whatever god or gods the supplicant believes in. It is also used without much hope of success. I'm speaking in general about religions,not just christianity. If a spell or circle were being used to achieve the desired results by calling on gods or goddesses in a carefully proscribed way,intending to enforce their aid,willing or not,to enforce you will,I would not call that prayer either. I have read the Mists of Avalon.