The Free On-line Dictionary of Computing (30 December 2018):
The derivation of new facts from known facts and inference
rules. This is one of the fundamental operations of
artificial intelligence and logic programming languages
Inference is a basic part of human reasoning. For example
given that all men are mortal and that Socrates is a man, it
is a trivial step to infer that Socrates is mortal. We might
express these symbolically:
man(X) => mortal(X).
("if X is a man then X is mortal" and "Socrates is a man").
Here, "man", "mortal" and "socrates" are just arbitrary
symbols which the computer manipulates without reference to or
knowledge of their external meaning. A forward chaining
system (a production system) could use these to infer the
simply by matching the left-hand-side of the implication
against the fact and substituting socrates for the variable X.