A surety bond is the classic bail bond. When you can't afford to pay the court the entire bail amount in cash, a licensed bail bondsman posts it on your behalf. In exchange, you pay a one-time premium — a percentage of the total bond — and the bonding company guarantees the full amount to the court.
This is how most misdemeanors and felonies are handled. You put down a fraction of the bail, we take on the rest of the risk, and your loved one walks. A co-signer (indemnitor) is usually required to guarantee the defendant shows up to court.