What is the difference between friendly flirting and serious flirting?

I believe "friendly" flirting is meant to be light hearted and without a hope of anything more...especially sexually.
I believe "serious" flirting is meant to be the process before seduction happens...where the end goal is sexual activity of any kind....

The orgasm?

One of them will get a black eye because their other half hits you. The other you get a black eye because your partner has hit you...

Friendly is when it occurs haphazardly, serious is when it's nearing a pathological nature.

Serious includes touch