Pitch and Tempo
This effect allows both pitch and tempo to be changed independently. Pitch is how high or low the notes sound. Tempo is how fast or slow the notes are played.
Pitch is measured in cents, which is one-hundredth of an equal tempered semi-tone. One semitone is 100 cents, and one octave is 1200 cents.
Tempo is measured in percent of the original file's tempo. Fifty percent is half speed, and 200% is double time. Tempo also affects the total duration of the file.
If you want the traditional, analog-style pitch control, turn on the "Link Pitch & Tempo" checkbox. This turns off the pitch shifting compensation and just varies the playback speed.