Considering removing the fat under my chin. What is this and why does it happen? (Photo)

Hello, hope you are well. These examples are showing different things. The first few photos are demonstrating platysmal banding which occurs naturally very frequently as people age. This takes place when the anterior edges of a thin sheet of muscle in the neck called the platysma become visible under the skin. It can be corrected with a procedure called a 'playsmaplasty.' In some cases, overly aggressive surgery can skeletonize the central neck structures and expose these or other muscles with a central concavity which would be referred to as a 'cobra neck deformity.' The next couple photos show what appears to be postoperative scarring after a neck lift which can occur for a variety of reasons, but the most likely probably being excessive removal of subcutaneous fat which causes the skin to scar down to deeper neck tissues. In any case, the lesson is that a healthy amount of fat must be left behind after surgery to ensure a smooth natural looking contour and to prevent scarring.
Best,Dr. Tower

Some people as they age have little fat in the neck and so other aging changes show, like the lady in your first photos. The next lady has had facial surgery at some time in the past, and her neck is aging faster than her face. Perhaps she tried something smaller than and facelift which is not holding up well on her neck. She has had surgery in the past. If fat removal is conservative, you should do well.

What you’re seeing are platysma bands. As you age, the neck muscle called the platysma sags forming the parallel bands hanging under the chin. This is treated with surgery by suturing the muscle in the midline as well as out on both sides to tighten the muscle. Liposuction can be done at the same time to remove excess fat. Consult with an experienced plastic surgeon to discuss your options.