You want to have the lowest hand, and your hand cannot have matching suits. so if you have
Ac 2s 3d 4h you have the nuts, but if you have Ac 2c 3d 4h then you really only have a three card hand with Ac 3d 4h which is beaten by any 4 card hand of all suits (aka a badugi)
You also can't have a pair, and straights don't matter.