A surety bond is not insurance, though it is sold by insurance companies and regulated as insurance. It is a three-party promise in which the party who pays expects to be paid back. This article explains that structure and why it changes everything downstream. It covers bid, performance, and payment bonds; the Miller Act that protects subcontractors on federal projects because they cannot file liens; the ninety-day notice and one-year suit deadlines that end most claims; who counts as a protected claimant and who does not; the indemnity agreement contractors sign without reading; and what happens when a surety takes over a defaulted job.