OGC Web Map Service (WMS)
The OGC Web Map Service (WMS) defines an interface that allows a client to retrieve maps of georeferenced data. In WMS context, a map means a graphical representation (jpeg, gif or png files) of a geospatial data meaning that a WMS service does not give access to the data itself. It is used for mapping purposes and can be combined with other WMS services.
OGC Web Map Service Specification: http://www.opengeospatial.org/standards/wms