Thanks Stefan.
That's the simplest explanation I have yet to hear.

Stefan wrote:
QNE means 1013.2 (i.e. 29.92). You set it above a certain altitude,
which differs from county to country, or above the transition altitude
at controlled airports, in which case the transition altitude is
published. On some airports it stays the same all the time, on other
airports it varies.

Below this altitude, you set either QNH (altitude above MSL) or QFE
(altitude above airport level). Again, this varies from one place to
another.