When a state is entered the animation assigned to it is being played. In addition to animations, the graph allows extra properties, events and effects to be linked to a state. These get executed as well, when a state is entered. It is irrelevant whether the state is a regular state (with Selection Criteria) or a transitional state. For many modifiers, it is also irrelevant whether the state has an animation assigned to it, or just serves as a Hub State.
Along with the animation for example, a facial sequence or a sound can be played, a particle effect spawned, or an event be send back to the game code. The latter can also be useful to tell the game a state is being left, for example after a reload animation has finished, actually increase the number of bullets on the game side.
The Modifier System is extendable. You can create your own Modifiers to add additional functionality to your graph.
For more information on how two create custom modifiers, see the AnimationGraph Programming Reference.
To add a new Modifier to the graph, use the "Graph" Menu, just as adding Inputs, States and Views. A Popup Menu offers all available Modifiers. The Modifiers that are currently present in the graph are listed in the Modifier Tab, usually located as a register with the States and Inputs tabs.
For a full list of Modifiers and a short description of their functionality, see the Modifier Reference, which lists all the available Modifiers that ship with the SDK Build.