The cutlass is a short sword that was used around the 16th century as butcher knives.  Later the cutlass became favored by pirates for hand to hand combat in confined spaces like on the decks of ships.

The dagger was a very small sword.  It was ideal for a surprise attack because it was small and easy to hide.  It was also used for fighting hand to hand when a long sword would not be useful.

The rapier is a sword that is very thin.  This sword was mainly used for dueling between two pirates.

The long sword was a lot like the cutlass except for the fact that a long sword has two cutting edges and the cutlass has only one.  Another difference is that the long sword is longer than the cutlass.