from h+ Magazine:
This is not simply a case of using infrared light, a camera, and eye movement to move a cursor and click buttons: Text 2.0 infers user intentions and enhances the reading experience in far more complex ways.
Reading certain words, phrases, or names can trigger the appearance of footnotes, translations, definitions, biographies, even sound effects or animations. Ask how a word is pronounced and you get a verbal answer.
If you begin skimming the text, it fades out the less important words. If you glance away, a bookmark automatically appears, pointing to where you stopped reading.