A state diagram, sometimes known as a state machine diagram, is a type of behavioral diagram in the Unified Modeling Language (UML) that shows transitions between various objects.
State machine diagram is a behavior diagram which shows discrete behavior of a part of designed system through finite state transitions. State machine diagrams can also be used to express the usage protocol of part of a system.
State diagrams have been used in programming to describe the various possible states that a system can be in for decades. They also quickly show which states lead to each other, and what triggers a change of state.