I just recently checked out a book from the library that addresses the different kind of calls. I am by no means an expert on the subject but from what I understand there are essentialy 5 different kinds of calls that can be used at different times of the the year.

The first and most versital is just a short soft social call that is used by bucks and does a like. Another is the doe/ fawn bleat that can be used to attract deer during pre-rut.

The last three are more for use during the rut, the doe in estrus call, a trailing buck call and a tending buck call. The 2 later calls are similar but one is used while the bukcs are chasing a doe and the tending call is used when a buck is staying with a hot doe and is used to warn would be suitors.

I'm sure someone with more experience in with calling can elaborate on this a little more.