Web Map Services (WMS), one of the first OGC web services created, provides a method for dynamic raster generation served over the Web. They are a compromise between the flexibility of WFS and the speed of Tile services.
There are several iterations of WMS, and QGIS supports most of them. To use a WMS, you need to give QGIS the GetCapabilities URL of the service that you want to view data from.
Find a WMS service that you want to use and copy the GetCapabilities URL. In this recipe, we can use the Geoserver demo website (http://demo.opengeo.org/geoserver/web/).
Open the Add WMS dialog.
Create a New connection.
Assign a Name of your choosing and paste in the URL (http://demo.opengeo.org/geoserver/ows?service=wms&version=1...