I think you're a little confused.
An RNAV approach is a non precision approach based on a minimum required navigation performance. In some cases where (GPS) or (GNSS) is included in the title then satellite navigation must be used as the primary navigation source in order to fly the procedure. Where no such label is included in the procedure title then RNAV using any sensor is allowed. The procedure name may include a RNP number in which case your EPU or ANP must be lower than the value stated in order to fly the approach.
An ILS is a precision approach which must be flown using localiser and glide slope as the primary navigation source.
GPS is the commercial name of the US satellite navigation system. GNSS is the term used where any approved satellite navigation system may be used.