Shark School notes that rays and sharks have many of the same basic body parts. Several of the differences between sharks and rays concern the differing shape and function of similar body parts.
Many sharks and rays have long bodies. Shark bodies are slender, whereas ray bodies are flat. The flattened bodies of rays help them live closer to the bottom of the ocean floor.
Both sharks and rays have pectoral fins. However, sharks use their fins for both lift and steering while rays use them to swim. The ray typically does this by flapping or fluttering the fins in order to achieve motion. Sharks and rays each have tails.
Sharks use their tails to swim by sweeping their tails from side to side. Ray tails are more narrow than shark tails and some of them lack fins. Rays use their tails to balance and steer their bodies. The sharp barb that many rays have at the end of their tails is used for protection.
Finally, both sharks and rays have gill openings. The gill openings on sharks are on their sides in front of their pectoral fins. Gill openings on rays, by contrast, are on the underside of the head. A ray's pectoral fins are located over and in front of its gill openings.