There are two main ways in which the body heals a wound. Where the edges of the wound are neat and are able to close back together (either naturally, or with the help of sutures), the healing that ensues is called "healing by primary intention". When the edges of the wound cannot be closed, or where skin has been removed, the body needs to create tissue to cover this wound. This is called "healing by secondary intention".
Summary of the process of wound healing :
1) Inflammatory phase. Immediately after injury - 5 days
When the skin is cut, the blood vessels constrict, to prevent the loss of too much blood. As the blood begins to coagulate, the blood vessels dilate, allowing fluid to pass more easily through them, creating a build up of tissue fluid around the wound, and causing the area to look and feel inflamed. Most of the other processes going on here are to help the body clean the wound and prevent infection, but growth factors are produced which prepare the body for producing collagen.
2) Proliferative phase. 2 days - 3 weeks
The wound will still be in the inflammatory phase when this second phase occurs. Collagen is laid down by the body in the space between the wound margins. To minimize the area of scar tissue needed, the wound will begin to contract, and the wound margins will draw closer, reducing the width of the scar by up to 50%.
3) Remodeling phase. 1 week - 2 years
The granulation tissue created by the body in response to the injury is slowly converted to scar tissue. Collagen is being formed and destroyed all the time in a healing wound, as the body converts one type of tissue to another. Normal skin cells from the edges of the wound multiply and migrate inwards, further reducing the area of the scar. The majority of this change will occur within the first two months, but the scar will continue to mature for around two years.