I know there are other Voice Programs out alike Ventrilo, Mumble (mentioned in Enjin post), etc. But I personally approve of TeamSpeak 3 over them. There are also additional extras alike adding avatars, bb codes in channel descriptions allowing to add images, colored text, client descriptions, etc.
On management wise, there are server groups and channel groups, each added to specific clients by admins. Under advance client permissions you can allow certain people to talk in channels and join channels, but to further simplify from advance permissions, you can just simply add a password to a channel to prohibit people from joining.
There can be so much to explain but I rather you search then get me to explain, go to http://www.teamspeak.com/ to find further information.
Edited by CrucialOutcast, 01 May 2012 - 04:59 AM.