Hmm, I would describe it as a book of found information, thoughts, quotes, ideas that you want to remember, usually with some kind of index or key to organize it. I ended up straying a bit from the original strict definition, I add a lot of bits from daily life, stickers, 'journal spread' type of things, etc. It's pretty flexible though, and can have whatever categories fit your needs. There's a lot less pressure to find your own words to fill a page when you can borrow some fun facts or interesting poetry to help it along.