Thanks to everyone for getting in and replying. Much appreciated.
So, RNAV and RNP are both Performance Based Navigation(PBN) and work around the same principle - use nav aids/radio beacons around them to fly from point A to point B rather than flying over each nav aid/beacon. The difference between the two being, RNP requires on board monitoring and alerting system and will alert the pilot if he happens to pass the minimums for that particular RNP route.
Do correct me if my understanding to this is wrong.
Also is the RNAV coupled with the INS/IRS for navigation purposes ?