In the past year or so, the DDoS attack has become the hacktivist's tool of choice, while it also remains one of the easiest ways for script kiddies and botnet bosses to cause e-havoc. We all have a general idea of how they work—computers send a boatload of traffic to a site's servers until they break. (I like to envision them exploding, but I don't think that actually happens.) But beyond that, they're a bit of an abstract thing to understand.
The videos above and below do a great job clearing the issue up. They were created with a tool called Logstalgia that visualizes website access requests like a game of Pong. Flying in from the left are requests—individual users trying to load a page or picture or whatever—and the bar on the right simulates the site's servers, gliding up and down to meet each request, process it, and send the data back.
According to Mashable's Stan Schroeder, who dug up the videos, the top video was created by VideoLAN developer Ludovic Fauvet, who visualized a DDoS attack on VideoLAN's servers. Compare it to the video below of how normal traffic works. In the DDoS video, the server is stuck dealing with a massive influx of traffic on one random page, while all the normal requests going unanswered. In the normal one, the server is able to accept and send back all of the requested data that's needed.