An automaton is a simple model of a computer. An automaton has some form of input, has some form of output, has internal states, may or may not have some form of storage, is hard-wired rather than programmable.
An automaton that computes a Boolean (yes-no) function is called an acceptor. Acceptors may be used as the membership criterion of a language.
An automaton that produces more general output (typically a string) is called a transducer.