Behaviorals make “fake spaces” and liberate animators. The below tools are behavioral controls useful for animators.
Paths abstract acceleration from the position of the mesh. An example would be tracing a finger over a surface.
Coordinate many bones very easily. An example of drivers are fingers and eyelids.
Constraints translate between spaces. An example would be a world-space Forward Kinematic (FK) head.
Expressions are the only tool that knows (cares) about time. An example of an expression is a scheduler.