There are 4 basic types of RNAV procedures available:
VOR/DME
DME/DME
GNSS
RNP (Required Navigation Performance)
The 1st three specify the source of navigation data to be used - the last specifies the accuracy to be achieved, and doesn't care how you do it - therefore allowing the full capabilities of the aircraft to be untilised. Any of the 1st three can be assigned an RNP value.