Staphylococcus (sometimes called “staph”) is a group of bacteria that can cause a multitude of diseases. Staph infections may cause disease due to direct infection or due to the production of toxins by the bacteria.

Boils, impetigo, food poisoning, cellulitis, and toxic shock syndrome are all examples of diseases that can are caused due to Staphylococcus.
Symptoms and signs of a localized staph infection include a collection of pus, such as a boil, furuncle, or abscess. The area is typically tender or painful and may be reddened and swollen.

Methicillin-resistant Staphylococcus aureus, known as MRSA. Seems like it is a type of Staphylococcus aureus that is resistant to the antibiotic methicillin and other drugs in this class.