I need a plugin described like this. What is it called?

So I know this plugin exists because I saw it on another wordpress website.

So the plugin works like this:

There is a Rectangle Box and when you left click the title of the box it expands into a bigger box where you can read text. What it is basically it hides text in a box, much like a spoiler box. What is this plugin called?

Thanks,

Jason McCoy
NerdOrGeek.com