Plain English Meaning

How high you are and how fast you are going through the air. In level flight these two things are linked through power: add or reduce power and one or both will change unless you also adjust pitch.

Full Definition

The two primary performance results that respond to power changes in straight-and-level flight: altitude is the aircraft's vertical position above a reference, and airspeed is the aircraft's speed through the air. In the power-control context, these two values are managed together because a change in power setting affects both, and the pilot must adjust pitch attitude to determine which one changes and which one is held .