What is the Call availability option?

What is the "Call availability" option?

The "Call availability" option allows all Pro users (Basic, Moderator or Administrator) to turn "on" or "off" the permission to receive IVR calls. If a Pro user is available to receive IVR calls, then he/she can turn “On” the call availability option. Conversely, if a Pro user is temporarily busy or unavailable to receive IVR calls then, he/she can turn “Off” the call availability option.