Lets say you took the Vikings, Eagles and Giants in your parlay...

You'd either get a 3 teamer at 6:1 (average odds for that bet), or 3 2-teamers (Vikes/Eagles, Vikes/Giants, Eagles/Giants) at 2.8:1 odds (again, average odds for a 2 teamer).

The idea behind it is that you still get something back if 1 of your 3 picks loses. But its kind of a sucker bet...

If you bet $15 on a 3 teamer, it would return 90 in profit for $105 total
If you do $5 on the 3 2-teamers, it would return $42 in profit ($14 in profit for each 2 teamer - 5 x 2.8) for $57 total. If you won 2 out of the 3 games, you'd end up losing a buck ($15 investment - $14 on the one parlay you hit).