What do all those fins do?

Dorsal Fin: Helps maintain balance while swimming.

The Pectoral Fin: Allows for abrupt changes in side-to-side direction and speed. It also acts as a brake to decrease speed while swimming.

Pelvic Fin: Stabilizes the fish while swimming and allows for up-and-down movement in the water.

Anal Fin: Stabilizes the fish while swimming.

Caudal Fin: Moves, propels or pushes the fish through the water.

Adipose Fin: Not present on a lot of fish species. Its purpose is unknown. Trout, salmon and catfish have an adipose fin. It is the small, thick, fleshy fin located between the dorsal and caudal fins.