Wolf is a creature type.
In magic, there are two common varieties of wolves: Regular wolves and werewolves.
Wolves often occur as creature tokens. If they appear as such they are always 2/2. Wolves from earlier sets may have power and toughness ranging from 1/1 all the way to 7/6. But in recent sets the only exception is Watchwolf. Other wolves are printed as 2/2 creatures.
By legend werewolves are supposed to be anthropomorphic wolves that spread by biting humans that become like them. It is unclear if it happens like that in Magic. However, werewolves are of the type human wolf, indicating that at least part of them is human.
Werewolves as a creature type were first introduced in the Innistrad set.