Basically means they are being held without bail. In other words, no amount of money will secure thier freedom. Thier lawyer can request a bail hearing where the judge can set the bail amount or deny bail altogether. Usually depends on the offense and the potential flight risk of the inmate. Example; O. J. Simpson was denied bail when charged with two counts of murder. So he remained in custody until and during his trial and was only released after a not guilty verdict was reached by the jury. There are also some crimes that are known as non-bailable offenses.