Hi Ejector,
Two-dimensional (2D) instrument approach operations, using lateral navigation guidance only, e.g. a VOR,NDB,RNAV approach or
Three-dimensional (3D) instrument approach operations, using both lateral and vertical navigation guidance, e.g. an ILS,GLS, Lnav/Vnav approach.
https://www.airservicesaustralia.com...up/a14-h26.pdf