In Buddhism, they mean the same thing. The word Buddha comes from the Sanskrit root budh which means to be awake, to understand or to know. A Buddha is one who is awake, one who understands or one who knows.
Although we think of nirvana as meaning enlightenment, it actually means cessation or extinction. It literally means blowing out, like blowing out a candle. It is the extinguishing of the craving that causes rebirth. It can also mean perfection or the great peace.
The Sanskrit word we translate into English as enlightenment is bodhi. Bodhi also comes from the root budh, so the words awaken and awakening are closer to the true meaning.
©2016 Stephen L. Martin
Photo: Buddha’s statue near Belum Caves Andhra Pradesh India