Overview. A carbuncle is an infection of the skin that may be filled with pus. The infection usually occurs deep within your skin and involves your hair follicles. It is also called a staph skin infection.Carbunculosis is the name given to more than one carbuncle.verview. A carbuncle is an infection of the skin that may be filled with pus. The infection usually occurs deep within your skin and involves your hair follicles. It is also called a staph skin infection.