Ease-in will start the animation slowly, and finish at full speed.

Ease-out will start the animation at full speed, then finish slowly.

Ease-in-out will start slowly, be fastest in the middle of the animation, then finish slowly.

Ease is like ease-in-out, except it starts slightly faster than it ends; thus, is the fastest default rendering all things held equally with the smoothest transition speed start to end.
=============================================================================