Mom taught you that when you were done playing that you should put your toys away. That was good advice for the floor of the playroom when you were a kid, and it's still good advice now, even when a lot of your "toys" are programs running on your computer. You've been busy editing multiple documents with your favorite word processor and decide you're done, so you close them all. But does that mean that the application itself is closed? Depends; sometimes closing that last application window will kill the app itself, but often, it just sits there, still running–and taking up memory and other resources–but it's not benefitting you at all. Mom probably wouldn't be happy.
RedQuits is a tool that can help make sure that doesn't happen to you. Once it's up and running, closing that last application window automatically closes the application itself. No more "orphan" apps running and taking up resources when you think you've put all your toys away.
RedQuits is a free download. You can use it on your Mac (OS X 10.6 and later).