Human: What is the difference between a crocodile and a alligator? Assistant: 
The main difference between a crocodile and an alligator is in their physical characteristics. Crocodiles are generally larger, with longer snouts, more prominent ridges on their back, and thicker tails than alligators. Alligators have broader heads and shorter snouts than crocodiles, as well as thinner tails. Additionally, crocodiles tend to live in saltwater habitats while alligators prefer freshwater rivers and lakes.