A tummy tuck contours the belly by removal of extra skin. Sometimes, the extra skin hangs only in the area of the lower belly. Other times, the extra skin overhangs both the lower belly and also the skin above the belly button. If this happens, there may be fullness of the area above the belly button as well. For both situations, the extra skin can be removed through the lower abdomen, and then the skin is stretched taut to create a better contour.
The question next however is whether liposuction would be helpful as well. The best area to assess this is by pinching the sides of your lower rib cage. This area, called the flank, is not well treated with a tummy tuck on its own, because the scar has to taper off at the front of your hips. However fullness of this area indicates a significant component of both extra skin AND fat that is causing the contour issues of your belly. The downside of adding liposuction is obviously increased cost. However the benefit is correction to a better aesthetic outcome for patients who have a significant amount of both problems.