ASP.NET Web Controls
The Web controls reside in the System.Web.UI.WebControls namespace, which is available to all Web Forms pages automatically. They provide a range of functionality, from simple data entry to complex data validation. Two classes are considered to be base classes of ASP.NET server controls: System.Web.UI.Control and System.Web.UI.WebControls.WebControl.
Web controls fall into eight categories: input, display, action, selection, databound, rich, validation, They have properties, methods, and events that can be accessed at run time from code running on the server.