Choose a building and touch a floor and it tells you more details of the building. You can use it when you want to know a car model, an insect name, what kind of food is served at a restaurant and how much, who built a bridge, etc. etc.
so you can use it this way when you want to check the meaning of a word in the newspaper, book, magazine, etc. It would be much easier to read a real book. You can use the dictionary, wikipedia, thesaurus and anything else available on the web. What do you think?