Bail is money that some criminal defendants are required to deposit to guarantee that they will return to court if released from jail while their cases are pending. The judge sets the amount, and the money is deposited with the clerk of the court. It is returned after the case is finished.

Bail may be posted as "cash," or through a bond. A bond is a legal contract that requires someone to pay money if a defendant fails to return to court. It is guaranteed by the assets of the person who posted it, such as real estate, savings, or valuable personal property. A "surety" bond is one in which another person or a bail bond company – the "obligor" – undertakes to ensure that a defendant returns to court, upon penalty of losing the bail amount if the defendant fails to do so. An "appearance" bond is one in which the defendant him or herself is the obligor.

Most commonly, the court will direct that bail be posted in cash or as an insurance company bail bond. Often the bond amount will be higher than the cash alternative, because courts are aware that bond companies generally accept well less than 100% of the face value of the bond as security. Once cash bail or a bond is posted, the court has the authority to order a hearing (a "surety hearing"), to determine whether the bail money came from legal sources.

Although the law appears to require that the judge give at least two alternative ways of posting bail, a number of judges will set "cash only" bail. Unless a lawyer can persuade a reviewing court to change such an order, bail will then have to be posted in cash rather than as any type of bond.