A server control in classic ASP.NET is a component that dynamically renders a segment of markup to the client. Controls can be written in markup or coded, and can be bound to data and participate in different phases of the ASP.NET request-handling lifecycle. Out-of-box examples range from the simple (CheckBox which wraps the HTML input checkbox) and more complex (GridView which can be bound to various data sources and has built-in paging and sorting).