What WinMin does is that it stays in the background, searching the window titles for a matching search criteria. It then hides any window matching the critera, thus giving back control to the previous active window.
Many websites use pop-up windows for commercials.
These windows are very annoying as they can pop up more than once on your visit to a website. This is where WinMin comes into play. Just enter the title of the annoying window into the search string file and start WinMin. Now the window will be minimized whenever it pops up. Getting rid of it and letting you focus on the website, instead of the commercials.