What is Nirvana? Who was the Buddha?

What is Nirvana:
http://www.thebuddhagarden.com/nirvana-meaning.html

https://aeon.co/essays/nirvana-can-seem-an-exotic-metaphysical-idea-until-you-look-closer

https://science.howstuffworks.com/science-vs-myth/extrasensory-perceptions/nirvana1.htm

Who was the Buddha:
http://www.thebuddhagarden.com/who-was-the-buddha.html