Destinations are provided by various modules. If you don't have
these modules installed, you will not see these destinations. Current
modules are:

Core

Provides the ability to send a call to an Extension, or an extensions Voice Mail box directly.

Queues

Lets you send a call into a Queue, which is an intelligent Ring Group.

IVR

This lets you jump to a specific Digital Receptionist IVR.

Time Conditions

This lets you do the equivalent of an 'IF', and you can pick two
different destinations depending on the time of the call. See Time
Conditions for more information.

Ring Groups

A Ring Group is a group of phones that ring simultaneously or sequentially. A dumber version of Queues

Conferences

Lets you use a standard tele-conferencing application. Please read Conferences before using

Misc Destinations

This lets you enter a number, just as if you dialed it on one of
your phones. Useful for making an "outside" number (such as a mobile
phone) a destination.

Custom App

You can create your own application using the standard Asterisk
Dialplan language in the file /etc/asterisk/extensions_custom.conf, and
reference it with this. An example would be:

custom-count2four

exten => s,1,SayDigits(1234)

exten => s,2,Hangup

After placing this in /etc/asterisk/extensions_custom.conf, you can send callers to this by using 'custom-count2four,s,1'