I would gander the most common is microdermabrasion, which is also known as mechanical exfoliation or micro-resurfacing. You are basically having your skin gently sanded to removing the thicker, uneven outer layer. It works best for sun damage and small scars.

Laser surgery which can use a laser to do what dermabrasion can but without actually blasting the skin with anything. The laser sloths off the top uneven area so new skin can grow under it. It also decreased chance of infection as well as a “bloodless surgery.

Then there are chemical peels, which use several acid or caustic solutions or methods to kill off the top layers of the skin to they die and flake away naturally, or can be buffed off, allowing new growth to simulate underneath. There are risks, but the surgeon doing it can walk you through it.

There are other methods using creams, compression or injections but they are not as widely used as the laser and dermabrasion.

The main method of most scar removals is to allow new skin to be stimulated or grow by removing the damaged skin from the area that is scarred.