What does it mean?
The changing parameter might be level, delay, pitch, filtering, or pan. A greater Depth does not necessarily mean a louder output.
ExampleA larger Tremolo Depth makes the level dips deeper.
How the meaning changes between controls
Guitar Synth
The Motion control becomes Vibrato, Ensemble, Chorus, or Strike depending on the voice. Check the active model; it is not identical modulation across every voice.