I am new to Visual Studio development.
Occasionally I hide the toolbox on the left side of window of Visual Studio Express. But then, sometimes, I would like to use it.
How does one reactivate and display it?
Ctrl-Alt-X is the keyboard shortcut I use, although that may because I have Resharper installed - otherwise Ctrl W, X.
From the menu: View -> Toolbox.
You can easily view/change key bindings using Tools -> Options Environment->Keyboard. It has a convenient UI where you can enter a word, and it shows you what key bindings include that word, including View.Toolbox.
You might want to browse through the online MSDN documentation on getting started with Visual Studio.