Bats fly, which does make them different from most mammals. Species in this order are divided into two suborders. Megchiroptera, which includes the various species of flying foxes, and Microchiroptera. Flying foxes use echolocation, a kind of natural sonar for locating prey and other objects. Megachiropteran bats are found only in Europe, Asia, etc.
Microchiropteran bats do echolocate and are a much more diverse and widely distributed group.
Bats are indeed beneficial to people. In many cultures, bats are a symbol of good luck and fortune. In our own western culture, this for the most part is not so. Many view bats as unclean, disease carrying, symbols of evil. In reality, bats are actually very gentle, and will only bite if attacked or threatened or improperly handled.