Fallers are the teams that are completely out of the playoffs. They just try to win games to not look as bad. They've already started falling off the cliff, so they try flapping their arms to make the fall take a longer amount of time. Right now, this is like the Colts, 1-13 with a third string starting every game (I guess they're thanking Kerry Collins right now).
Cliffhangers are the teams that have a chance, but not a very big one, that they can make it to the playoffs. It's kind of obvious, but most of these teams end up as fallers. Many teams in the NFL are like this, such as the Patriots, Eagles, Cowboys, or the Bills.
Runners are those really good teams that need one, or zero wins to make it to the playoffs. These guys are running away from the cliff, they don't need to go back and help other teams, because they could be pulled back down. This is a team much like the 13-1 Packers. It's too bad they lost their perfect season, though.
So basically, if you look at the NFL the way I do, you see the setup of teams as fallers, cliffhangers, and runners. If you see it the way everyone else does, you see it as bad teams, okay teams, and good teams. It could be used either way.