Bats are not reptiles, they are flying mammals of the order Chiroptera. Mammals are a clade of warm blooded animals that have hair or fur, three middle ear bones, mammary glands in females, and a neocortex (region of the brain). They also give birth to live young. Bats have forelimbs that form webbed wings, making them the only mammals naturally capable of true and sustained flight.
Reptiles on the other hand are cold blooded creatures that often have scules, horny plates, or scales and reproduce by laying eggs that later hatch. Examples of reptiles include snakes, turtles, lizards, crocodiles, alligators, etc.