Land , Water or Both

amphibians stay under water when their  born, then above water when they are  older. but still  go in the water during the day. when they are young they have gills. when they get older they get lungs . their are over 4,000 different amphibians. the classes are toads, frogs, salamanders, newts, and caecilians or blindworms .Amphibians evolved from fish about 400 million years ago, when the amount of dry land on Earth increased greatly. Certain fish adapted to these changing conditions by gradually developing limbs to crawl with and lungs to breathe with. Such organisms, capable of life both in water and on land, came to be called amphibians, a name that means "double life." Amphibians were the first vertebrates (animals with backbones) to live on land. However, they returned to the water to breed. The largest variety of amphibians occurred about 360 to 230 million years ago, when the environment was continually alternating between wet and dry conditions. Many of the species that developed during this period no longer exist. The groups of amphibians that survived to the present day can be traced back no further than 200 million years.

taken from: http://www.encyclopedia.com/topic/amphibian.aspx