The basic idea is "Rapid Serial Visual Presentation": It keeps your eyes comparatively at rest at a central focal point, and sequentially displays the words at a rapid-fire clip.
Try it out: Copy and paste a big block of news, literature, or homework in there...and see how fast you can plow through it. I read some looooong articles in 2-3 minutes!
Interesting thing to note: I tried Spreeder on a long bit of "comedy" text. Doesn't work at all -- you lose all sense of timing and pacing. But for factual, dryer text...works like a charm.
Interesting (nerdy) thing to note: Am I the only one to remember that rapid serial visual presentation is how the Bene Gesserit used to send communiques in Frank Herbert's "God Emperor of Dune"?