The fins of sharks are used for stabilizing, steering, lift and swimming. Each fin is used in a different manner.
There are one or two fins present along the dorsal midline called the first and second dorsal fin. These fins help the shark from constantly rolling around. These two fins may, or may not have spines. When spines are present, they are used for defensive purposes, and may also have skin glands with them that produce an irritating substance.
The pectoral fins are located behind the head and extend outwards. These fins are used for steering during swimming and help to provide the shark with lift.
The pelvic fins are located behind the pectoral fins, near the claoca, and are also stabilizers.