I found this one host it only have 1 MySQL Database. I do't understand about the number of howmany MySQL Database we can have. Does one MySQL Database mean you can only have one forum/questbook/or anything that require MySQL Database?

It's not neccessary to have a lot of DBs, but programs that require a DB can all be placed into one. But if you do get more it's nice to spread the programs out onto the number of DBs that you have. One DB should be sufficient enough to run a forum, a blogging software, & a guestbook, plus other lil scripts you may want to add (i.e. tagboard, etc).

Edit: It's always nice to find a host that supplies more than 1, but that's MHO.