Kicker light...what's the main purpose?

I have been reading about Kicker lights. Is the main purpose of this to be another "fill" light to go along with the main, hair, etc.

They're typically used more like a hair light... to add a bright edge to separate the subject from the background more, or to simply add another level of lighting interest which can help add form to the subject. I often times think of kickers as being brighter than the main and therefore would not be considered a fill light at all.