Frogs usually have smooth skin covered in mucus and long legs. Toads typically have shorter legs and rougher, thicker skin adapted to drier habitats. Most frogs lay their eggs in clusters, while toads usually lay their eggs in long strands.
Frogs and toads are amphibians belonging to the order Anura. The distinguishing mark of this order is that adults do not have tails, except for the genus Ascaphus. They also have skeletal adaptations for leaping. There is no hard and fast scientific distinction between frogs and toads, and some anurans exhibit characteristics of both groups.
There are over 4,000 species of anurans, divided into 25 families. Anurans have the widest range of the three living orders of amphibians, and they live everywhere except the polar regions, some oceanic islands and extremely dry deserts. They inhabit a wide variety of habitats, including rain forests, mountaintops, deserts and swamps. Adults may live in the water, at ground level or in trees.
Most anurans reproduce by laying large numbers of eggs in water. After the male releases sperm over the eggs, the fertilized eggs eventually hatch into aquatic larvae called tadpoles. All anurans undergo metamorphosis from the juvenile to the adult form. In some species this takes place in a parent's brood pouch. In other species, metamorphosis takes place inside the egg.