Finite State Machines are commonly used in computer science and engineering to model the behavior of systems that can be in a finite number of conditions or states. They consist of a set of states, a starting state, an input alphabet, transition functions that dictate how to move between states based on input, and a set of accepting states that determine if the input sequence leads to a successful completion of the state machine’s operation. FSMs can be categorized into two types: deterministic (where each state has one specific transition for each input) and non-deterministic (where a state can have multiple transitions for the same input). Applications of FSMs are found in various areas including digital circuit design, software development, and protocols in networking.