Not much is known about Wobbufett's tail, other than the fact that Wobbufett keeps it hidden from others and tries to protect it from being attacked. It states in one of Wobbufett's pokedex entries that it's tail is very vulnerable to be being attacked, suggesting that it could be a weak spot of sorts, which would explain why Wobbufett keeps it hidden. Girafaig's tail (Which is actually a second head) is different, obviously serving the purpose of protection. It is stated in many of Girafarig's pokedex entries that it's tail has a brain of its own, and that it will attack others that come close enough to be heard or smelt. It also says that when Girafarig is eating the tail will mimic the head, so as to confuse attackers. Also, Girafarig's tail (second head) doesn't sleep, so it keeps watch while Girafarig sleeps.