WScript.Echo "Hello world!"
This displays a message on the console if run with
cscript.exe (the console host) or in a message box if run with
wscript.exe (the GUI host).
If you're using VBScript as the server-side scripting language for a web page (for classic ASP, for example),
Response.Write "Hello world!"
puts the message into the HTML send to the client (browser).
If you want to displays a message in the message box, you can use:
Msgbox "Hello World!"