Every state a character can be in inherits from the base CharacterState component. There are several general categories that states fall into:

Category Description Usage Examples
Idle The character's default state which they return to automatically after performing an action. Assigned to the Character.Idle field. IdleState
Action Something the character can do intentionally. Referenced by the Character Brain. JumpState
Reaction Something the character will do automatically in response to a specific event. Registers itself to be started by the relevant event so generally nothing else needs to reference it directly. IntroductionState
Special Multi-State is in a category of its own because it isn't really a state but rather is used to select from a list of other states. MultiState

There is no real distinction between those categories in the code, they are just here to help you understand how the various states fit together in a character.

Introduction A state used for a character to show off when they first spawn.
Multi-State A "state selector" which simply picks from a list of other states.
Idle The default states characters return to after they finish performing an action.
Jump The states used for different kinds of jumping.
Attack States used when the character is attacking.
Flinch A state used when a character gets hit by an attack.