The Learn To Sing Harmony courses around the country might vary in length and vary slightly in content. The organisers of the local courses will provide all the information that you need but you can expect to learn about :-
Posture and Breathing
Singing is a whole-body exercise, every part of you is involved.
The Vocal Mechanism
The muscles of your abdomen and chest force air from your lungs
between the vocal folds causing them to vibrate.