Frogs are NOT reptiles. Frogs are amphibians.
Although frogs have some similarities with reptilian animals, they actually part of the zoological class known as amphibians. One trait belonging to frogs and reptiles like iguanas is that they are cold blooded. As a warm-blooded human, you can regulate your body temperature. Neither a frog nor an iguana, for example, is able to maintain its body temperature. Therefore, these creatures rely upon the environment to be cool or warm. The similarities end there, however.
As an amphibian, a frog starts its life as an egg hatching in water. Frogs eventually move away from the water to live on land. Mature frogs return to wet areas to deposit their eggs. These eggs develop within the water, where they have soft shells. A frog lays a large amount of eggs to because many of them will not survive the process. Starting with more eggs ensures that more tadpoles hatch. Because reptiles have hard eggs, they typically hatch on land and not in water. You may have seen turtle or snake eggs in a nest. Reptile mothers typically don't lay as many eggs as frogs and other amphibians.
Frogs have a distinct life cycle that requires a metamorphosis between stages. Frog eggs hatch into tadpoles that breathe through gills, frogs then grow legs and their tails transform until a fully developed frog appears with the ability to breathe through lungs. In comparison, reptiles hatch from eggs into smaller versions of the adult. The major metamorphosis isn't something that reptiles experience.
The ability to breathe in water through skin contact can sometimes make frogs appear slimy or sticky when you touch their skin. Reptiles like alligators have dry, scaly skin when you touch them. Some frogs secrete poison through their skin. However, a reptile would have to bite you to inject poisonous venom.