The primary difference between a reptile and an amphibian lies in their reproductive methods and their adaptations to their environments. Reptiles, which include snakes, lizards, and turtles, are primarily terrestrial and adopt a more advanced method of reproduction, typically laying eggs that have hard shells. They are also ectothermic, meaning they rely on external heat sources to regulate their body temperature. In contrast, amphibians, like frogs and salamanders, often spend part of their life cycle in water and begin as larvae with gills. They undergo metamorphosis and generally have moist skin, which is essential for respiration and hydration, differentiating them from reptiles.