Do you mean staph infection? or rather, Staphylococcus. It is a bacteria that can cause diseases when infected into the body through your tissue. Often, it does not cause diseases but when there is a wound or damage in your skin, it can. The symptom of it is boils. It can cause such diseases as pneumonia, blood poisoning, TSS, etc.
Staph commonly lives in the nose. Say you rub your nose, then scratch a scab or cut, you can get a staph infection. When I was a kid, i had an ant bite on my knee, and i scratched it and somehow it became a staph infection. My doctor told me that it is common so you should use plenty of antibacterial soaps and hand sanitizers.