A tummy tuck tightens fascia and removes extra skin. There are several types of tummy tucks, basically falling into three categories:
Mini tucks just below the belly button - OK for scar revision but does not tighten skin or fascia above the belly button. Short incision.
Hybrid tummy tuck(R) - tightens fascia all the way up, removes minimal skin. OK for patients with very little loose skin. Small incision.
Full tummy tuck - removes lots of skin and tightens the deep layer. Long incision.
Liposuction by any method removes skin only. I am totally unconvinced that laser / VASER do any significant tightening of the skin, and usually it is more of a marketing ploy to patients who hope to avoid the incisions of a tummy tuck.
Don't be conned into getting liposuction alone if you have lots of extra skin, or if you have a loose deep fascia. You will only be lumpy and disappointed.