The velocity is the intensity of a sound, such as whether you pluck a guitar string or press a piano key hard or softly. Pressing the key softly creates a low-intensity, high-velocity sound; plucking a string hard creates a high-intensity, high-velocity sound. You can use velocity scaling to "fade out" at the end of a song.
The Velocity action allows you to scale velocity for all notes between specified points for a selected track.
Click on the image below for details about each control: