Call Screening is part of the Reach Me feature and is enabled under the Call Handling section found on the Reach Me Web page in your User Preferences. When Call Screening is enabled:
callers are prompted to record their name before a call is forwarded.
the recorded name is played when you receive the forwarded call, and you can accept or reject the call.
If rejected, the caller is told that you are unavailable and is routed to your Messaging mailbox.