What is Android InCallUI? What is Android InCallUI? I keep seeing it under apps I've used.

I googled it and I keep seeing it related to this xPrivacy Pro software. I have an Android ZTE Z812 phone and am wondering how I find out if this software is installed on my phone and how to access it?
InCallUI = In Call User Interface.  It handles the display when you're in a call; it has nothing to do with privacy software and you can't uninstall it since it is a core system app.