There is a longer texts at the end of each of the three distinct sections, informing you about the specific font you just saw, as well as its included features.
You can skip between these sections be clicking on the little markers on the right.
All the other text is there to show you the fonts and their features in action, be it ligatures, be it international diacritics or different font weights.
But here I think they overdid it. There is too much going on, I can't tell where I am, and I have no idea what I'm supposed to get out of it. (Probably doesn't help that I don't remember much German from high school, but even then I'm not sure the actual text content would be all that helpful).