Hi coffee. I know there's a lot of jargon that gets bandied about here, and I'd be happy to try to clarify it for you. It would be helpful to know a bit more about what you already understand, though. Do you know what a range is? Do you know what a continuation bet (c bet) is? I'll do my best here:

1. A bluffing range is all of the hands a player would bluff with in a given situation. I don't know that it really makes sense to talk about this range having a top or bottom, because usually bluffs are all very weak hands (a value range is more likely to have a top and bottom, because not all value bets are equally strong). But I guess the top of a bluffing range would be the best hands a player would bluff in a given situation, and the bottom would be the worst hands.

2. A bluff catcher is a hand that can only beat a bluff. Often, especially on the river, one player will make a large bet representing a very strong hand. He will do this with both very strong hands (his value range) and bluffs (his bluffing range). His opponent would have an easy call if he himself had a very strong hand. Usually, however, his opponent needs to call with some hands that can only beat bluffs or he risks making bluffing very profitable for his opponent. These weaker hands that call hoping to be ahead of a bluff are his bluff catchign range.

3. A continuation bet is a bet made by the pre-flop raiser on the flop. The idea is that, by raising pre-flop, he has represented a strong hand, whereas the player who called him probably does not have a strong hand or that player would have re-raised. Thus, on any given flop, the pre-flop raiser will usually bet all of his strong hands plus some bluffs. This entire range of hands that he bets on the flop is his c-betting range.