An example of this principle can be some complex object, which, after some movement, suddenly stopped — some of its parts are still moving (as it calms down).
An example can be a character who stops suddenly, and his ears or tail continues to move by inertia
Regarding making HTML5 banners - this can be an animation of a word in which there is a letter “I” with a dot.
The word was moving and stopped, but the dot was still moving a little so the animation will look more interesting.
