Timeline

This is a Pro-Only Feature: you can try it out in the Unity Editor with Animancer Lite, but it will not be available in runtime builds unless you purchase Animancer Pro.

Unity's Timeline package is a sequencing system that can manage things like animations, audio, particle systems, and other events in order to develop things like cut-scenes and cinematics.

Timeline Assets are normally played using a PlayableDirector but Animancer can also play them with a PlayableAssetState:

PlayableDirector PlayableAssetState
Outside of Animancer, Timeline Assets are played using a PlayableDirector component as explained in the official Timeline Tutorial. Inside Animancer, Timeline Assets are played using a PlayableAssetState as explained in the Platformer example.
Even with Animancer, this is still often the best way to play Timelines that control multiple characters. This is the recommended approach for Timelines that only control a single character that is already being controlled using Animancer since it fits right in with that character's other animation states. As with all other States, you can get a PlayableAsset timeline; and manually create a new PlayableAssetState(timeline), but Transitions are often easier to use.

Bindings

Timelines can contain multiple "Tracks" which each control a different object in the scene. Since a TimelineAsset is an asset, it can't directly reference scene objects so whatever plays it needs to specify its Bindings to assign the object each track controls.

If the first track of the TimelineAsset used in a PlayableAssetState is an Animation Track, it will automatically be applied to the Animator playing that state so you do not need to set a Binding for it.