“Bail” is a deposit of money that courts require from criminal defendants. The court holds the deposit to ensure that the defendant keeps all court appearances. Bail amounts vary based on the charges and severity of the crimes and sometimes the courts do not allow bail at all. “Bailing someone out” is when you provide the money so that the defendant does not need to remain in jail.
If you have a friend or loved one that you wish to bail out, first you will need to get a bondsman.