Not just form controls like buttons and text boxes, but also special-purpose controls like a calendar, menus, and a tree view control are included in Web server controls. In comparison to HTML server controls, web server controls have a more abstract object model that does not always mirror HTML syntax.
Server controls can be used in a variety of ways. For example, we can use them to validate user input or to filter out invalid data from our database.
Three types of server controls:
HTML Server Controls - Traditional HTML tags.
Web Server Controls - New ASP.NET tags.
Validation Server Controls - For input validation."
Server controls can be found in the HTML section of a document, while web controls can be found in the section.