The Royal Courts of Justice, commonly called the Law Courts, is a building in London, which houses the Court of Appeal and the High Court of Justice of England and Wales. Courts within the building are open to the public although there may be some restrictions depending upon the nature of the cases being held. Note that these are not the highest courts in the land - this distinction is reserved for the House of Lords.
Those who do not have legal representation may receive some assistance within the court building. The Citizens Advice Bureau (http://www.nacab.org.uk) has a small office In the main entrance hall where lawyers provide free advice. There is usually a queue for this service. There is also a Personal Support Unit where litigants in person can get emotional support and practical information about what happens in court.
The main criminal court, housed separately, is the Central Criminal Court, popularly known as the Old Bailey.