When a person appears in court accused of a crime, there is often a preliminary hearing to decide if there is a case to answer and the actual trial takes place at a later date.
Until this trial happens, to keep control of the accused person who has not yet been convicted, they may be "remanded on bail", meaning they put up an amount of money which is forfeited if they fail to appear for trial.
Alternatively, if the court decides that they might interfere with witnesses, leave the country or otherwise fail to appear regardless of bail they may be "remanded in custody" meaning they are imprisoned until the trial.