Plain English Meaning

The aircraft's computer shows you a suggested up-or-down path to follow, but it is only a helpful hint. You still have to fly the published altitudes yourself using the regular altimeter -- the path on the screen is not officially approved guidance.

Full Definition

A vertical navigation function in which the flight management system or GPS computes and displays a recommended descent path to help the pilot manage altitude on an approach or arrival, but does not provide approved vertical guidance for the approach itself. The pilot remains responsible for complying with all published altitude restrictions using the primary altimeter, and the displayed path is for situational awareness only.