Wikipedia: "In Classical Antiquity, an oracle was a person or agency considered to be a source of wise counsel or prophetic predictions or precognition of the future, inspired by the gods. As such it is a form of divination.
The word oracle comes from the Latin verb ōrāre "to speak" and properly refers to the priest or priestess uttering the prediction. In extended use, oracle may also refer to the site of the oracle, and to the oracular utterances themselves, called khrēsmoi (χρησμοί) in Greek.
Oracles were thought to be portals through which the gods spoke directly to people. In this sense they were different from seers (manteis, μάντεις) who interpreted signs sent by the gods through bird signs, animal entrails, and other various methods."