The Megalodon had teeth that were serrated which would have help slicing through the flesh of their prey. This would have been extremely helpful as some evidence would suggest that the Megalodon mainly preyed on whales (however it also preyed on sirenians, dolphins, and pinnipeds). We can guess that whales were a big part of their diet as a lot of whale vertebrates have been found with huge bite marks which match that of a Megalodon. As well as this, Megalodon teeth have been found next to chewed remains of whales.
The Megalodon was thought to have live in warm watered areas. This was because, being a shark, and so cold blooded, it need a warmer climate. Teeth from this shark have been found all around the world, including Europe, North America, South America, Australia, New Zealand, Japan, South Africa, Malta and India.
Why did it change/become extinct
It is hard to believe that a creature as big and powerful as the great Megalodon could have become extinct after ages of thriving. However, creatures (especially large ones) can become extinct fairly easily. One of the key factors of the Megalodon's extinction is thought to have been an extreme climate change. If the climate, and so temperature of the sea, had dropped rapidly, then places were the Megalodon could thrive would become more and more scarce. As well as their being fewer areas where the Megalodon could survive, there would also be a 'food shortage' a huge number of creatures that would have been prey would have died out. Since the Megalodon was such a big predator, this would have been a real problem. The combination of been frozen and starved could well have caused the extinction of such an animal.