what exactly scar is?

The scar have many colors, which is the pale pink, brown, or silvery patch of skin that grows in the place where you once had a cut, scrape, or sore. A scar is your skin's way of repairing itself from injury. Most people do. Why? Because a lot of things leave behind scars - from falls, like the one Holly had, to surgeries.
Scars are part of life and they show what you've been through. For some people, scars are special. A kid in your class might have a scar on his chest because he had heart surgery as a baby. Or you might have a scar from the chicken pox.