An OLE server is any application that can perform action (typically, edit or play) on an object when the OLE libraries inform it that a user has activated an object associated with that server. When the user activates an object—typically, by double-clicking on the object—the server application starts, and the user edits or plays the object inside a window of the server application.
Some applications can be both clients and servers for linked and embedded objects—for example, Microsoft Word for Windows can act as a client or as a server for OLE objects.