State diagrams are diagrams that show the states of a system or process and the transitions between those states. They are used to model the behavior of a system and to understand how the system will behave in different scenarios. State diagrams can be used to represent a wide variety of systems, from software
From Wikipedia
A state diagram is used in computer science and related fields to describe the behavior of systems. State diagrams require that the system is composed of a finite number of states. Sometimes, this is indeed the case, while at other times this is a reasonable abstraction. Many forms of state diagrams exist, which differ slightly and have different semantics.