The Guards are a group of regiments — large, named groups of soldiers — in the British army. They began as the soldiers who guarded the king or queen; that is how they got the name. Today they still do ceremonial work: the red coats and tall black hats outside the palace are Guards. They are also real fighting regiments, not only a show. There are several, with names like the Grenadier Guards and the Coldstream Guards. You write it with a capital G because it is a name, not just any people who guard a door. In Britain, for a young man from a rich or old family, becoming an officer in the Guards has long been seen as a smart, respectable job — a bit like joining a very old club that also goes to war. Though actually, other countries have “guards” too; this English word, with the capital, points to those British ones. Ordinary security guards at a shop are not the Guards.