The bail system in the United States can be quite complicated and can also vary from local jurisdiction to jurisdiction. In general, there are some common characteristics to all forms of bail. Bail, itself, doesn't even come into play unless one has been arrested for a crime. Depending on the severity of that crime, there could be a few potential outcomes to that arrest.
After an Arrest
The first is that the police might release the arrested party and not file any charges. This is effectively as if the arrest never happened (from a purely legal perspective). The second is that the police could book the arrested party and release them on their own recognizance or with a citation. In either case, the release is predicated on the arrested party's implicit agreement to show up in court at a later date. Another possibility is that the police arrest, book, and then release the arrested party, and the corresponding district attorney's office decides to dismiss the case (and, therefore, the charges). As with the police not filing charges, in this scenario, it is also effectively as if the original arrest never occurred (from a legal standpoint).
The last scenario is that the police arrest, book, and then either set bail themselves or bring the arrested party before a judge of the court to be arraigned. During the arraignment, the judge can both decide to allow bail and also decide the amount of the bail. Virtually all crimes have locally codified bail schedules. The judge must stay within these schedule amounts when setting bail.
Paying the Bail Amount
If bail is granted, the arrested party can pay the bail amount to the court in cash or via another means accepted by the court; such as signing over a lien to a real-estate property or vehicle or paying by credit card or other assured non-liquid assets. This allows the arrested party to remain free whilst awaiting their day in the court. The court tends to prefer allowing bail, when possible, because it frees them from the expense and responsibility of keeping the person incarcerated until their trial date. The bail amount itself acts as a so-called "good faith" action by the arrested party to agree to appear in court. Should the person not show up to court, however, the court will rule the bail previously posted as forfeit and will keep it in its entirety. After a person's trail, the bail amount can typically be refunded back to the party who paid it.
Using a Bail Bond Professional
In cases where the arrested person is granted the ability to post bail to remain free whilst awaiting trial but do not have any assets accepted by the court with which to post said bail, they might seek out a licensed bail bonds company. The bail bonds company agrees to pay the full bond amount to the court should the arrested person not show up in court; and the arrested person pays fees and/or charges to the bail bonds company for their services via a signed, written contract. The typical bail bonds fee amounts to anywhere from ten to fifteen percent of the full bail amount. For example, ten percent of a $10,000 court set bail amount would be $1,000. The bail bonds company keeps this amount as their service fee regardless of the outcome of the trail.
For more information, contact a professional who provides bail bonds.