About using ArcGIS services in ArcMap
ArcGIS for Desktop users create geographic information that is captured and preserved as geodatabases, map documents, geoprocessing toolboxes, image files, and so on. Each of these can be published and shared as GIS web services using ArcGIS for Server. For a full list of services that are available, see What types of services can you publish.
ArcMap is designed to be able to connect to ArcGIS for Server and work with its services. For example, when you click Add Data, you can browse to an ArcGIS for Server connection and add map and image web services into your table of contents, just like you would with any other data source.
Web services may be used in more subtle ways, too, such as when performing geocoding or network analysis operations. As you use ArcMap, be aware of places where you might take advantage of web services to get functionality or information beyond what is available on your local computer.