A namespace is used to organize classes into a hierarchy, often to group types with related functionalities.

In PowerShell, the System namespace is implicit.

The System.AppDomain type was used previously; this command, used when introducing assemblies, can be shortened:

[AppDomain]::CurrentDomain.GetAssemblies() 

The same applies to types with longer names, such as System.Management.Automation.PowerShell:

[Management.Automation.PowerShell].Assembly