Cases often appear in the court's lists several times before there is a hearing, or before sentencing occurs. These occasions are known as "callovers" or "mentions" and are used to find out how you will plead, and how many hours or days will need to be allocated for a hearing.
Cases can go ahead on the "mention day" only if you are pleading guilty, as neither the arresting officer nor any prosecution witnesses will be attending court on the mention day. If you are pleading not guilty, the case will have to be adjourned (postponed) to a date when the court has time to hear it and all the witnesses are available.
You can also ask for your case to be adjourned from the "mention day" even if you want to plead guilty, to allow time for character references and pre-court reports to be obtained. It is useful sometimes to apply for an adjournment in order to ask the police in writing for all of the evidence they plan to reply on. This is essential in appraising the strength of the case against you.
If you are unprepared for your case it may be better to get your case adjourned. If it is a "mention day", you will be automatically entitled to at least one adjournment.
If you are in any doubt as to whether the hearing date is a "mention day" and whether you are on bail, you should telephone the court.