Some of the best fitness and strength benefits come from abdominal training, This is commonly called Core strength. In other words your mid section or trunk. There are four major abdominal muscle areas to work out. Also your back muscles should be exorcised in conjunction so as to avoid an imbalance. Correct balance between back and abdominals is important for good health and athletic power.
You need a competent instructor to discuss and show you these exorcises fully and properly.
1. Psoas. Large internal muscle has no great visual effect but is important for strength and posture - especially your back. This is conditioned by doing sit-ups. However, it is important to do sit-ups properly. Legs bent, back flat down. Fingers on temples.
2. Frontal abs (Rectus abdominis). This is the six pack and can be conditioned in a variety of ways. It has a good visual effect. This area is worked by bringing your chest in towards your groin.
To condition front abs - Crunches, leg raises and hanging bar exercises are the most common. Sit-ups do also have an effect but are less efficient than the above.
3. Side abs (Transversus). This is the main muscle group to tuck-in your gut. It is placed either side of your frontal abs and works like a corset. You will get more 'looks' benefit from this one muscle than by all the others put together. It also helps provide abdominal pressure to help keep your back straight.
4. Internal & external obliques. The final group is next to your elbows and works by pulling your shoulder towards your hip and in twisting actions. However, working these incorrectly will thicken your waist and this is often the last thing most people want from an abs routine.
Core strength is vital for athletes and a full session with regular training on core strength is probably the single most important aspect of any exorcise routine.