A surety is one serves as a guarantor on bond or other obligation such as a debt. If the person signing the bond performs their obligation, the surety does not have to "do anything." If the person pays their debt, the surety does not have to pay it. If the person signing the bond does not perform as indicated on the bond, the surety is at financial or legal risk. The the person who is supposed to pay the debt does not pay, the surety becomes obligated.