A plaque is a sign attached to a surface that commemorates a deceased person or an event, or explains something about a place. You will have seen them at war memorials, or sometimes on park benches to indicate who donated it.
Good plaques are often made of bronze, which is a combination of copper and tin and doesn't rust like iron-based metals. For this reason the writing on bronze plaques lasts longer and is therefore ideal for locations that are exposed to the elements. You could get a plaque to put in your garden to remember a former pet - perhaps by attaching it to his/her favourite tree. Most of us however will encounter plaques in cemeteries or in crematoriums where the ashes of the departed are stored and labelled with name plaques.
Historical events and places of special interest are also marked with plaques. Mozart's house, for example, or the site of a city's first hospital or theatre, which may have been long forgotten save for the bronze plaque attached to a new wall to highlight the history of the place. Many public benefactors are remembered on plaques in parks, zoos, opera houses and botanical gardens around the country.
The price of a plaque depends on how ornate the design is, the number of words that need to be engraved on it (along with any decorative elements) and the size. Make sure that if you want the plaque and its significance to last, you need one made from the best possible material; that is, polished cast bronze.