Resistance. Mrsa is just a staph aureus that has a new gene that renders it resistant to beta-lactam antibiotics; for the most part, it will present the exact same as a "regular" staph infection, and will respond to other antibiotics the same as non-mrsa. It is difficult to call one regular because in most of the us, about 50% of all staph aureus is now mrsa. Only way to tell for sure is lab culture.
Resistant bacteria. Mrsa stands for methicillin resistant staph aureus, and it refers to a particular strain of bacteria that has developed resistance to the antibiotics traditionally used to treat it. Treatment of MRSA usually requires multiple antibiotics, but a lot depends on the site of the infection.