Happy Hours Specials

Can someone please explain when it does or doesn't count as happy hour?

Like, to get the happy hour special... do you have to order within the happy hour? Or do you have to pay within the happy hour? Or both? Or is every restaurant different?

Because it just seems like people try to get a happy hour discount, and then one way or another, get screwed out of the discount. Or the bill gets screwed up.

Like the special are just a distraction and they hope you'll forget.