VIP stands for "Very Important Person". You can add this status to individual entries in your directory. That way you will be able to assign special ringer melody to these entries and can then discern them from other (normal) calls.
Open the directory and select an entry. Press the right side of the control key (C2: Press the menu key.) to open the menu. Scroll to menu item "VIP Entry" (C2: "Mark as VIP") and confirm with "OK".
Then you will be able to assign a spezial ringer melody to this VIP entry.
Hint:-The VIP entry will only be recognized when a) the number is passed on from the phone company and b) the CLIP function has been switched on at your phone line!
-It is possible to assign different ringer melodies to the different VIP entries.