In computer science oracles are considered to be special machines, that can provide answers to non-computable problems. In terms of that definition, all modern computers are not oracles. This fact is true, because all problems that computers solve basically come down to performing some sort of computation, based on certain finite input parameters.

Therefore, oracles, or oracle machines, by definition ¹, can compute the uncomputable. In plain words, oracles can provide answers to the questions that are not mathematical problems. According to that terminology and the main point of reference to Alan Turing's Theory of Computation, the internal workings of an oracle are unknown. The the oracle, however, will always provide one and the same output as a response to one and the same input.

Much like Turing's original oracle machine, an æternity oracle produces an ouput result, however, only to a given question. So, by itself an individual æternity oracle is not universal, but numerous oracles can be created, so that a multitude of questions can be answered. The oracle's output result is provided by the person, who has launched the oracle This person who has committed, by means of the æternity token, to provide an answer during a certain time frame, specified at the launch of the oracle.

Because at this point in time, there are no hardware oracles, æternity oracles aim to provide a trustworthy YES or NO answer to every possible type of question, whose YES or NO answer can be substantiated with real-world data. So again, the human brain will be a part of the process performing a check on the question's answer. That is natural because the human brain is an instantiation of the oracle machine. Every single oracle resides on æternity's blockchain.

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¹ "Systems Of Logic Based On Ordinals", A. M. Turing, 1936, Seeley G. Mudd Manuscript Library, Princeton, NJ, Accessed on 05.05.2017, Link