Frogs and toads are amphibians. Both are part of the classification order Salientia or Frog Order. That order is subdivided into families that include true frogs Ranidae, treefrogs Hylidae and toads Bufonidae. Toads tend to have thicker, drier skins and are suited for a more terrestial lifestyle. We tend to easily recognize them as different from other frogs and the term "toads" is part of the common vernacular. However, the thinner-skinned, more moisture-dependent Ranidae and Hylidae frogs are not as easily distinguished from each other. True frogs such as green, pickerel, leopard, wood and bullfrogs are called "frogs" in common vernacular as are the treefrogs such as peepers and gray treefrogs.
One often hears frogs and toads more often than seeing them. Their lovely songs can be quite distinctive, you can often make an identification from that alone. I have been able to include audio files for some of the species listed here. You may find audio for the others by exploring the links section.
Bullfrog
Gray Treefrog
Green frog
Northern leopard frog
Pickerel frog
Spring Peeper
Wood frog
American Toad 
Fowler's Toad