A scar is a mark left on the skin after a wound or injury has healed. Scars are a natural part of the healing process. Most will fade, although they never completely disappear.
A stretch mark is a type of scar developed when the skin expands or shrinks rapidly in a short period. The collagen and elastic fibre rupture during the sudden change in the skin, and when the skin heals, stretch marks may appear.
Pregnancy or rapid weight loss/gain could promote the development of stretch marks. The early stretch marks tend to be red, pink, purple, or reddish-brown. They may appear slightly raised and can be itchy. With time, the colour fades, and they become narrow indented streaks.
It depends on the person's genes, fat percentage, age or skin thickness; the appearance of stretch marks may be more noticeable than others if one's skin becomes thinner and loses elasticity as aging.
Often the recommended treatment for stretch marks involves three or more treatment methods. Just like any other scars, they may never disappear altogether, but treatment may make them look less noticeable more quickly.