What kinds of notes do people take in the Bible?

I seen a bible the Priest at my Parish had and it had no notes in it... And he told me it was one of the first bible's he's had... And then I saw this one ladies bible and she had paper hanging out of it, post its, everything... I never had the nerves to ask her what kinds of things she wrote in it, but I really would like to know what kinds of things people write in their Bible...