Questions related to the NLA (Non-Linear Animation) editor in blender.

The Non-Linear Animation editor (NLA editor) is used for managing small animations (or Actions). These actions can be layered and combined into longer animations.

From the manual:

The NLA editor can manipulate and repurpose actions, without the tedium of keyframe handling. Its often used to make broad, significant changes to a scene's animation, with relative ease. It can also repurpose, and 'layer' actions, which make it easier to organize, and version-control your animation.