Plastic surgery is a general term for operative manual and instrumental treatment which is performed for functional or aesthetic reasons.
Common reconstructive surgeries are: breast reconstruction for women who have had a mastectomy, cleft lip and palate surgery, contracture surgery for burn survivors, and closing skin and mucosa defects after removal of tumors in the head and neck region. Sex reassignment surgery for transsexual people is another example of reconstructive surgery.
Plastic surgeons have developed the use of microsurgery to transfer tissue for coverage of a defect when no local tissue is available. Tissue "flaps" comprised of skin, muscle, bone, fat or a combination, may be removed from the body, moved to another site on the body and reconnected to a blood supply by suturing arteries and veins as small as 1-2 mm in diameter.
There is a definite gray area between reconstructive and cosmetic surgery. Many of the techniques of cosmetic surgery are utilized in reconstructive surgery to improve cosmesis.
Cosmetic surgery is a very popular avenue for personal enhancement, as demonstrated by the 11.9 million cosmetic procedures performed in the U.S. alone in 2004. As for any operation, cosmetic procedures involve risk, and should therefore not be undertaken lightly. Within the US, critics of plastic surgery note that it is legal for any doctor, regardless of speciality, to perform "cosmetic surgery", but not "plastic surgery". It is thus important to distinguish the terms "plastic surgery" and "cosmetic surgery": Plastic Surgery is recognized by the American Board of Medical Specialties (the only official entity overseeing physician certification in the United States) as the subspecialty dedicated to the surgical repair of defects of form or function -- this includes cosmetic (or aesthetic) surgery, as well as reconstructive surgery. The term "cosmetic surgery" however, simply refers to surgery that is designed to improve cosmetics, or appearance. (One could argue that reconstructive surgery always has some cosmetic aspect to it, because form and function are often both important in plastic surgery repairs.) Thus there is no real art of "cosmetic surgery": it is a catch-all commercial phrase that laypeople understand easily and non-plastic surgeons eagerly use because they are not allowed to use the term "plastic surgery".