When someone is arrested, there's a process that allows him to receive temporary release from jail in exchange for monetary payment. This payment is called bail, a commitment expected of the defendant to make all scheduled court hearings in exchange for staying out of jail. Bail is typically refunded to the accused (if he pays) or the bail bond agency when the court date appearances are over.
Usually, the amount of bail is set more than the accused can pay. It is in these instances that bail bonds can prove useful, with the accused or his family allowed to pay just a percentage of the bail amount while the selected bail bond agency takes care of the rest. Courts typically refund the original bail amount if the accused appears for all of his court dates, so in the cases that go well, the agency gets its money back, along with the percentage paid by the accused, as its profit.
The bail bond process usually goes this way: A bail bondsman will meet with the accused (and his cosigner if he has one) to inform the agency of the required fee to post the bond. Once the fee has been collected, and the agreement signed, the bondsman posts the bond for the principal amount of the bail. The jail then forwards the bond to court where it will be held in trust. The principal bail will be refunded to the bondsman, as long as the client appears in court as scheduled.