Frogs and toads belong to the order Anura. Anura means tailless amphibian.
There are three smaller orders and they are:
Just out of interest, the word 'amphibian' derives from two Greek words: 'amphi, meaning 'both' and bios meaning 'life'.
This is a very often asked question about these creatures. It is also a difficult question to answer.
It is best to remember that when these two words were 'invented' there were only two sorts of anura that were recognised, those being the frog, later known as Rana temporaria, a moist, slimy creature that jumped, and the toad, Bufo bufo, which was dry and warty and also walked.
Gradually, as more and more of these species came to be found in other areas, the two names - frog and toad - were applied to them according to their resemblance to one or the other 'frog' or 'toad'.
This was fine to begin with, but as more species were found, some of them bore resemblance to both the frog and the toad, having both moist, slimy species that also had dry warty relatives! Things are never simple in nature!
It can be helpful to think of tailless amphibians as 'frogs'. We do not really know an awful lot about the living frogs and toads, but our knowledge of their ancestors is even less! However, it is commonly believed that amphibians evolved from a group of fish known as lobe-fins (crossopterygians) which lived during the Devonian period which was approximately 350-400 million years ago!
It does seem most likely that the earliest amphibians evolved in shallow fresh-water lakes. Fossils of the oldest amphibian come from Greenland and were formed at the end of the Devonian period, which was about 350 million years ago (roughly!!).