The term "pitch" refers to the pitch you play or sing on your instrument. When you play the instrument, the MyGroove app detects the pitch of your played notes. The app will then give you appropriate feedback depending on whether you played the pitch correctly or incorrectly.
Learning how to pitch is crucial to developing a good ear and learning how to play an instrument properly. With regular practice, you will improve your skills and be able to play the right notes with the right pitch.