Difference in sharks?

Wikipedia has a good page on each of them (see links below). They are definitely different species. The blacktip shark is Carcharhinus limbatus and the blacktip reef shark is Carcharhinus melanopterus.

Blacktip sharks live in tropical waters all over the world, preferring relatively shallow water over continental shelves, but some dive as deep as 64 m. The blacktip reef shark is only found in the Pacific and Indian Oceans (and attached bodies of water like the Red Sea; not the Atlantic at all) and is usually found inshore in really shallow water.

Both species feed primarily on fish, but different species of fish because of their different habitats.

Both types of sharks are viviparous. It looks like the blacktip shark has annual reproductive cycles, while the blacktip reef shark can have annual or semiannual reproductive cycles, depending on where in the world the subpopulation lives.

Sharks have a skeleton made up of cartilage and dolphins have a skeleton made up of bone. Sharks have gills and extract oxygen from water (as fish have a tendancy to do) and dolphins ought to pass to the exterior and breath air (as mammals do). additionally, Sharks play hockey (and make it to the playoffs) and Dolphins play soccer.