Grafting is a procedure to replace or restore missing bone or gum tissue. A gum graft may be necessary to protect the teeth from the damaging effects of gum recession. It some cases however a person may choose to have grafting done to improve the aesthetic looks of ones smile.

Gum recession is the process in which the tissue that surrounds the teeth pulls away from a tooth, exposing more of the tooth or the tooth’s root. This can cause damage to supporting bone. Gum recession is a common dental problem; it affects 4% to 12% of adults and often goes unnoticed until it becomes more severe.

Many people don’t even notice that their gums have receded, because it is a gradual process. However, over time, an exposed tooth root can not only look ugly, but can cause tooth sensitivity, especially when eating cold or hot foods. Eventually, gum recession, if not treated, can cause tooth loss. To repair the damage and prevent further dental problems, a gum tissue graft may be needed.

(source: http://www.webmd.com/oral-health/guide/gum-tissue-graft-surgery)