Reptiles and mammals are very different in terms of appearance, but probably their main difference is the way that they regulate their body temperature. Mammals will have the natural ability to make sure that they will stay warm or cold because of how they are made.
Reptiles would need to rely on outside forces in order to stay warm when they are feeling cold. For example, they would need to rely on the sun's heat so that they would start to feel warm. The majority of mammals would also give birth to their young alive while reptiles would be laying eggs that would hatch when the baby reptiles are ready.
The main difference between mammals and reptiles is the way both reptiles and mammals regulate body heat and the way they reproduce. Mammals are vertebrates that give birth to their young ones alive. Mammals also have mammary glands, which they use to provide nourishment for their young until they are able to look for food for themselves.
Mammals have furs or hair and have sweat glands. Mammals have a part of the brain called neocortex that helps to regulate and produce body heat. Reptiles, on the other hand, reproduce by laying eggs. They do not give birth to their young ones alive. Reptiles are unable to produce body heat. They rely on external sources such as the sun to get warm.