Just like the ones in the good old days.
I'll let Wikipedia explain it, since they'd do a better job than me:
A Scaffold match takes place, in whole or in part, on a piece of scaffolding erected above the ring. The match can end in one of two ways; either with one wrestler pushing another off of the scaffold to the ring below, or with a wrestler retrieving a flag from the opposite side of the scaffold and return it to his own.
Scaffold matches have a (legitimate) air of danger about them, as the bump from such a height is hard to protect against and objects such as chipboard tables are placed in the ring to attempt to cushion the fall.