WMS Service

A WMS (Web Map Service) is a data stream for georeferenced bitmaps (JPEG, PNG, GIF) and vector graphics (SVG) that may correspond to one or more layers of geographic data. The data can be viewed but not searched since only a picture is transmitted, as opposed to the WFS (World Feature Service). Access to the service is done by means of a formatted URL (Internet address).

See http://en.wikipedia.org/wiki/Web_Map_Service