Beauty vs transform. Whereas cosmetic tends to refer to beauty treatments the term plastic encompasses both aesthetic and reconstructive treatments.
Reconstruction. Over the years, primarily due to the media, "plastic surgery" has become synonymous with "cosmetic surgery". However, in reality plastic surgery actually includes both cosmetic surgery (to change or improve physical appearance), and reconstructive surgery (eg for birth defects, after trauma or cancer).
Good question. Plastic surgery includes a number of areas: cosmetic surgery, hand surgery, craniofacial surgery, burn surgery, microsurgery, reconstructive surgery (e.g. Breast reconstruction after mastectomy, etc.) and, more recently, composite tissue transplantation (e.g. Hand transplantation.) cosmetic (or aesthetic) surgery involves starting with a normal feature and trying to improve it.