What is meant by app domain asp.net?

Refer to this link.
http://www.c-sharpcorner.com/UploadFile/nagryum/Appdomain07102007081415AM/Appdomain.aspx

Appdomain is just a interface between dif application.So tht thy can run independenly.

---->In application domains multiple applications can run in same process with out influencing
each other. If one of the application domains throws error it does not affect the other
application domains.

----> To invoke method in a object running in different application domain
.NET remoting is used.