WSH

What it is
WSH is the environment in which the script is executed. WSH takes care of feeding the script throught the correct interpreter and it provides the necessary interfaces (in the form of objects) to give the script access to command line arguments, COM objects, itself, environment variables, etc.

What it provides
WSH provides the following objects:

WScript
This is the WSH root object and it provides interfaces to the base level functions like th escript engine itself and the command line arguments. It also hold some of the interfaces that doesn't fit in anywhere else. (Examples?)
Provides:
Properties: Arguments, StdIn, StdOut, StdErr, Version, ScriptFullName, etc.
Methods: Echo, Quit, Sleep, GetObject, CreateObject, etc.

WshController
The WshController is used when remotely executing scripts on another machine.
Provides:
Properties: None.
Methods: CreateScript.

WshNetwork
Give access to the basic Windows networking functions like handling network drives and printers.
Provides:
Properties: ComputerName, UserName & UserDomain.
Methods: AddWindowsPrinterConnection, SetDefaultPrinter, MapNetworkDrive, etc.

WshShell
Provide tools to interact with the regular Windows user interface. Creating shortcuts, working with the registry, environment variables and running programs.
Provides:
Properties: CurrentDirectory, Environment & SpecialFolders.
Methods: AppActivate, ExpandEnvironmentStrings, RegRead, RegWrite, etc.