The word oracle in Greek can mean several related things. It means a god who predicts the future, like Apollo. It also means the priest who hears the message, and the message itself, and the place where the priest hears the message. Most often it means the priest or the message. The Greeks believed (like all other ancient people) that you could communicate with the gods at certain places, at certain times, through certain people, and that the gods would give you advice and maybe tell you what was going to happen in the future. But the Greek oracles had a couple of advantages too. First, you didn't just come and ask your question. You had to hang around the temple for a while, talking to the priests, so they could get to know you. And they could see you, not just hear your voice on the telephone. Second, everybody came to the same few oracles for help, and the priests at these oracles (unlike the Psychic Hotline) compared notes with each other. So if you asked "Should I get married?" and the oracle said "Yes," and then next week your girlfriend comes and she asks, "Will Gorgias ask me to marry him?" then the oracle already knows the answer to that one. There is every reason to think that the oracles were worth the money they charged.
http://www.cs.utk.edu/~mclennan/BA/L...reekfuture.htm