Reptiles and amphibians are distinctly related, but several primary distinguishing features clearly separate the two. They often inhabit different environments, and they have different life stages. At the basic level, amphibians must spend some of their time in the water, whereas reptiles do not have this stipulation. For reptiles, it is not essential for them to stay in the water to stay alive.
Lizards and snakes are ideally suited to dry environments such as deserts, and they rarely encounter moist areas. By contrast, many amphibians must remain moist to breathe. Although they do have lungs, they also take in oxygen through their skin. The skin means that they lose moisture easily as well, and some even die if their skin dries out completely.