Silver-gilt or gilded/gilt silver, sometimes known in American English by the French term vermeil (pronounced vehr-may; it's French!), is silver which has been gilded with gold.
Most large objects made in goldsmithing that appear to be gold are actually silver-gilt; for example most sporting trophies and many crown jewels are silver-gilt objects.
Apart from the raw materials being much less expensive to acquire than solid gold of any karat, silver-gilt objects are also noticeably lighter, as well as more durable. For objects that have intricate details, gilding greatly reduces the need for cleaning and polishing, and so reduces the risk of damage. Ungilded silver would suffer oxidisation and need frequent polishing wheras gold does not oxidise at all!