I'll start with an easy one.
grab an index card, or a piece of paper, or whatever's handy that's flat, and curl it a little bit. hold it at eye level, then raise it upwards until the bottom appears to be straight, but the top curves outwards.
they chose that angle because it looks like foreshortening, which is a drawing technique that implies size. it's used a lot in comic books, on occasion you see it done in movies.