A DFA, or Deterministic Finite Automaton, is a theoretical model used in computer science to represent and analyze the behavior of systems with a finite number of states. It consists of a set of states, a starting state, a set of accepting states, and transitions between states based on input symbols. DFAs are used to recognize patterns and validate strings in formal languages. DFAs are called "deterministic" because for each state and input symbol, there is exactly one transition to another state. This property makes DFAs efficient for processing input, as they can quickly determine whether a given string belongs to a specific language.