The automaton includes a variety of different states, and transitions. When automaton sees an input symbol, it starts a transition to another state, which is according to the rule of transition function (it takes the current state and the recent symbol as its input).

This theory of automata is also related to formal language theory. An automaton is a finite depiction of a formal language which can be an infinite set. Automata is often categorised by the class of formal language which they are able to recognize.

- Computation theory
- Formal verification
- Parsing
- Artificial intelligence
- Designing of compiler

An automaton is designed to process on some given sequence of input data in discrete time steps. At any point of time, the symbols that are given to the automaton as input forms a finite sequence of symbols, which comes to be known as a Word. An automaton consists of a finite group of states. At any time during the processing, the automaton is in some state or the other. At the time when input word is read, at that time the automaton is said to have come to a state of rest, and this state of rest is known to us as the final state. The acceptance or rejection of an input word depends on the final state. The group of all words accepted by an automaton is known as the language recognized by the automaton.

In a simpler way, an automaton is a mathematical object that receives a word as input and then makes a decision of accepting or rejecting it. An important role is played by the theory of automat in computational theory.

Continuous, Discrete, and hybrid automat:

The theory of automata usually defines the states of abstract machines but there also exist analog automata / hybrid continuous- discrete automata / continuous automata, all of these uses continuous time, analog data, or both of them.

- Deterministic/nondeterministic finite state machine
- Pushdown automaton
- Turing machine
- Linear bounded automaton
- Rabin automaton
- Streett automaton
- Muller automaton