DING! is basically another way to save money traveling SW. If you have downloaded it properly, a plane's wing should appear in your system tray (probably on the bottom of your computer screen.) When you get DING'd, you'll hear a sound like you do when you're flying and the steward/pilot come over the speakerphone. That tells you there's a special going on. They don't always last all day. It's usually for a set period of time. And I've gotten a DING virtually every day, but maybe not a lower price to the airports I travel to/from.
When you hear that sound, click on that icon in your system tray and it will bring you to a box telling you how long that special will last and will open to a new screen showing you the airports, etc.
No, you don't get the same price on their webite and when you get DING'd. In fact, DING prices don't even appear on their webiste, that's why you're encouraged to download this service.
Hope this makes sense!