The abdominal (Stomach) wall - commonly referred to as "Abs" - is composed of 4 groups:

• Rectus Abdominus
• Obliques (internal & external)
• Tranversus Abdominus

Abs are functionally very important, and act as a stabiliser in both Exercise and day-to-day movement.

It's widely agreed amongst fitness professionals that the most effective way to build abdominal strength and size is through lower-repetition, high resistance training - as opposed to the conventional approach of "Doing lots of crunches".