Interesting. In all the books I've read, Buddha is referred to as a singular person (whom I can remember his name right now). I've never heard of "Buddhahood," and I do a fair amount of reading on Buddhist topics.
Just for the record: (take it as a tl:dr of the wikipedia article)
Buddha is simply a state of consciousness were you enter (or realize in some versions of buddhism) Nirvana. In some versions of Buddhism, this makes you ascend, and exit the wheel of reincarnation. In others, it just gives you a higher state of thought, until you can exit the wheel of reincarnation.
The "first" Buddha, Prince Siddharta Gautama Buddha, was a young prince who left his royal home, and his power to realize the realities of the world (IIRC they were, Religion, Poverty, War and Famine or something like that). By accepting the world as it is, and thinking of it long enough, and accomplishing total selflessness, he ascended to Nirvana (basically you get there by realizing all is one).
However, some Buddhist thinks this is not the "real" Nirvana, because just saving yourself is your final selfish act, and those they have a Bodhisatva ideal. A Bodhisatva is a Buddha who decides to throw himself into the wheel of reincarnation again to help others achieve Nirvana. The Tibetans believe there are only a few Bodhisatvas that have ever returned, and that the most powerful of them, called Avalokitesvara, is Dalai Llama.
TL;DR The guy people usually talks about when talking about the Buddha is Sidharta Gautama Buddha.