A CNF is a point that defines a navigation track for a GPS, but why is it used when you there are GPS waypoints that are created to define a track?
From the AIM 1−1−17. Global Positioning System (GPS)
(2) A Computer Navigation Fix (CNF) is also a point defined by a latitude/longitude coordinate and is required to support Performance−Based Navigation (PBN) operations. The GPS receiver uses CNFs in conjunction with waypoints to navigate from point to point. However, CNFs are not recognized by ATC. … CNFs that do appear on aeronautical charts allow pilots increased situational awareness by identifying points in the aircraft database route of flight with points on the aeronautical chart. CNFs are random five-letter identifiers, not pronounceable like waypoints and placed in parenthesis. Eventually, all CNFs will begin with the letters “CF” followed by three consonants (for example, CFWBG).
As an example, the glide slope intercept for an ILS that I fly shows up in the Garmin 430 as a waypoint since the GPS requires a FAF to sequence to the MAP in order to conduct an approach. But it does not show up on the chart. (Remember that an ILS doesn’t have a FAF on the chart.) I have seen them on charts, but none come to mind right now.