Creating Pop-Up messages in Ubuntu Terminal?

Hello, I would like to know how to create pop-up windows using the Terminal is Ubuntu Linux, much like using VBScript in Windows to make pop ups appear. I am NOT talking about the "ECHO" command. I simply want to know how to make a pop-up info box.
Update: If it can't run in terminal, I understand that it might have to be a file, again, like VBScript, which doesn't run in CMD.
Update 2: Okay, I have successfully made a pop-up window, and even a question pop-up. If it is a question pop-up, how do I make something happen only when the user clicks OK?
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