ASP.NET UserControl is the new way of encapsulate all your code reuse in your web applications. Old way of doing this would be via SSI includes which can be very messy and very hard to maintain if your site grow. ASP.NET UserControl is infact the simplest form of ASP.NET control encapsulation. Because they are the simplest, they are also the easiest to create and use. Essentially user control is a grouping of existing server controls into a single container control. This enables you to group all your reusable part of webpage into UserControl. The basic example would be Login Controls, News Controls, Header Controls and etc.