How to represent AppDomain in ASP.NET?

Recently i attentened an interview.I have been asked to explain the "Application Domain" and the special purpose about the introduction of "application domain".

I explained :

AppDomain is a runtime representation of a logical process withing a physical process (win32) managed by CLR.

Special purpose :

Keeps high level application isolation ;fall down of one AppDomain never interrupt othe AppDomain.

But still the interviewer expects lots from me ? what are the additional points could i add further?

Thanks.

They might want you to talk about running different Application Pools and how that can affect your AppDomain as far as IIS and ASP.NET goes.

Example: By having your website run in it's own Application Pool, you reduce the risk of the website going down because some other application crashes, and vice versa, since it would be running in it's own process.

You should say about advanced security configuration options and also here is explanation in wikipedia, that is complete enough. Also here is more complex overview.