Reptiles can have claws and venomous teeth to defend themselves from predators. You won’t find these on a amphibian. Instead, the can secrete venom from their skin. Reptiles are also more aggressive defenders than amphibians. Reptiles are built for offense and amphibians are built for passive defense.
Amphibians have stages of development and change form and shape before reaching adulthood. Reptiles start out just as smaller versions of the adults. They don’t change other than growing larger.
Amphibians are known for their wet and smooth skin that can be sticky because of mucous glands. That’s why they always look wet even when they’ve been out of the water. Reptiles on the other hand tend to have dry scaly skin that is rough and bumpy.
Many times amphibians such as salamanders are mistaken for lizards and vice versa. There are also very large lizards, but the majority of amphibians are small. You won’t see an amphibian the size of a alligator or crocodile.
I have been interested in both since childhood and since they are two different types of animals, the science of studying is the same. Herpetology is the study or reptiles and amphibians. This doesn’t help the idea of helping remember there are differences between the two.