Telephony options for users in Lync

These are the options for Telephony when configuring a user in Lync:

Audio/video disabled
The user cannot make calls with audio and video.

PC-to-PC only  
The user can make only PC-to-PC audio or video calls.

Enterprise Voice  
The user can use the Lync Server 2010 infrastructure to route all incoming and outgoing calls. The user can also make PC-to-PC calls.

Remote call control  
The user can use Lync Server 2010 to control the desktop phone, and can also make PC-to-PC calls.

Remote call control only
The user can use Lync Server 2010 to control the desktop phone, but this disables PC-to-PC audio calls, and only enables the user to control his PBX phone from Lync 2010 to make PC-to-phone calls.


See also:
http://technet.microsoft.com/en-us/library/gg520988.aspx
http://technet.microsoft.com/en-us/library/gg413011.aspx
http://technet.microsoft.com/en-us/library/gg615048.aspx