An oracle was a person in ancient Greece or Rome who people believed could communicate messages from the gods. When rulers faced difficult decisions, like whether to go to war or where to build a city, they would travel to visit an oracle and ask for divine guidance. The most famous oracle sat in a temple at Delphi, where she would breathe sacred vapors, enter a trance, and speak prophecies that priests would interpret.

The word also means any source of wise advice or seemingly mystical knowledge. In everyday conversation, someone might jokingly call their knowledgeable grandmother the family oracle because she always seems to know what's going to happen or what people should do. A particularly insightful teacher might be called an oracle on difficult math problems.

In the world of computers and databases, Oracle is also the name of a major technology company, chosen because databases are like oracles: you ask them questions, and they provide answers from vast stores of information.

The key idea behind oracle is that it's a source you turn to when you need answers that seem beyond ordinary knowledge, whether that source is mystical, wise through experience, or simply very well informed.