What is Custom Control in ASP.NET and how to use it

Custom Control is nothing but controls build upon the basic ASP.Net Control.

Like For example you can build a GridView with some features you want.

For example a GridView with Delete Confirmation

And then compile it into a DLL and then add reference and use it.

http://www.tutorialspoint.com/asp.net/asp.net_custom_controls.htm

http://www.codeproject.com/Articles/28783/Your-First-ASP-NET-Custom-Control