Bats are Chiroptera - pteron mammals, whose forelimbs form webbed wings, making them the only mammals that can fly naturally and permanently. In contrast, other mammals that are said to fly, such as squirrels, opossums and colobus monkeys, can only glide over short distances. Unlike birds, bats don't flap their entire forelimbs. Instead, they flap their loose fingers, which are long and covered with membranes or patagonies.

Bats are the second largest mammal after rodents, accounting for about 20% of all classified mammals in the world. Among them, about 1240 species of bats are divided into two sub orders: large bats or fruit bats with low specialization and eating fruits; and micro bats with high specialization and echolocation. About 70% of bats are insectivores. Most of the rest are dieters or fruit eaters. A few species, such as fish eating bats, feed on animals other than insects, while bloodsucking bats are bloodthirsty or feed on blood.

Bats are found in most parts of the world, with the exception of extremely cold areas. They play an important ecological role in pollinating flowers and spreading fruit seeds. Many tropical plant species depend entirely on bats to distribute their seeds. Bats are economically important because they consume pests and reduce the demand for pesticides.