.NET Performance tab
Just like the .NET Assemblies tab, the .NET Performance tab is shown only on Windows Vista and higher when Process Explorer runs with administrative rights and the selected process is using the .NET Framework. This tab lists the AppDomains in the process and displays data from nine sets of .NET performance counters:
To see the values of the object’s counters, select a .NET performance object. The counters are updated at the currently selected refresh interval.
An AppDomain (Application domain) in .NET Framework provides an isolation boundary for security, reliability, and versioning, and for unloading assemblies.