Most amphibians, including most frogs, spend part of their life as a water animal and part as a land animal. Frogs are related to toads but differ from them in several ways. The section Kinds of frogs describes the basic differences between frogs and toads. The first frogs appeared on earth about 180 million years ago. About 3,800 species of frogs and toads have developed from these early ancestors.
Some species spend their entire life in or near water.
Others live mainly on land and come to the water only to mate. Still other species never enter the water, not even to mate. Many kinds are climbers that dwell in trees. Others are burrowers that live underground. Throughout history, frogs have been the source of superstitions.