Think could be considered a productivity tool for the Mac. It is an application that allows you to focus on one task at the time by eliminating any distractions from your screen. The app will show a list of running applications when it is first launched. This window is called the illumination panel. It looks like the screen that pops up when you press Cmd + Tab on your keyboard. When you click on one of the running apps, it will be shown, or illuminated, as they like to call it. When one app is illuminated, the other running apps will be hidden. They will be kind of blacked out, so we can probably say they are obscured. If you have multiple monitors, they will be affected as well, and most likely if you are running an illuminated app on your main monitor, the secondary one will be blacked out. You can set the color used to hide apps and you can even set the transparency level. By default, transparency is set low enough so that you can still see other running apps, but they don't become a distraction.
I found that this app worked very well out-of-the-box. It could be useful for when you want to really focus on a task. In my case, I simply run apps in full-screen mode when I don't want to be bothered by other apps.
Anyway, go on the developer's website and read all their usage examples to see if you need this.