Almost anyone who's been arrested will go through a bail hearing. The amount of bail that's set is the money that has to be paid in order for you to be released from custody — basically it's a cash promise that you will return and face trial.
However, many people cannot afford the bail that's set during this hearing. That's when a bail bond agent steps in — in return for a fee, the agent will pay your bail, so that you're permitted to get out of jail.