What is a server control in ASP.NET?

A server control in ASP.NET is a control that has the runat="server" attribute. The component is processed on the server, and its HTML equivalent stream is passed to the browser. Note that all server controls inherit from the System.Web.UI.Control class. The server side controls may be dragged to a web page from the standard toolbox. Note that HTML controls are not server side controls, but they may behave so if the runat="server" attribute is added to their source.