http://bytes.com/topic/c-sharp/answers/261960-appdomain-vs-process

What is exactly the difference b/w an AppDomain and a Process, they seem to
me very much the same -- boundary for an execution context with protected
resources.

Carlos J. Quintero [.NET MVP]
  
Posts: n/a
 
#2: Nov 16 '05

re: AppDomain vs Process

In short:

A process is a Win32 OS concept and it is the boundary for isolation of
native apps.

An appdomain is a .NET concept and it is the boundary for isolation of .NET
apps.

1 process can have 1 or more appdomains. Since processes are "expensive",
appdomains are a better solution for .NET applications, where the .NET
runtime (rather than the OS) can ensure the isolation.