This is to reshape the male chest wall. This may just involve liposuction alone or require the removal of the breast tissue under the nipple as well. The most extreme is the removal of some skin as well.
Sometimes there's a dip in the middle of the nipple (a cleft) which is a mild inversion, but also there can be a complete pulling of the nipple into the breast and this will not come out, this is a grade 3 inversion.
Tummy Tuck, Full or mini (Abdominoplasty)