Types of Altitude

is the altitude above the surface, also know as, AGL. Above
Ground Level.

Absolute altitude

is the actual distance above mean sea level, or, MSL.

True altitude

altitude corrected for non-standard day pressure.
It is the altitude that is indicated when the altimeter is set to standard
pressure (29.92 "Hg).
Needed for most performance tables/charts.

Pressure altitude

altitude corrected for non-standard day pressure AND non-
standard day temperature.

Density altitude

altitude read directly from the altimeter (uncorrected) when it
is set to the current altimeter setting.

Indicated altitude