Wikipedia is a Wiki website where lots of people can contribute with content. That means that anybody can write anything, and even delete what other people write. Wikipedia claims to have over 200,000 articles in English. Wow!
The rules of different Wiki frameworks differ but a central feature is that the text you write quickly links to other pages. This also encourages you to write something about the new odd words you introduce. Words like "is", "the" are normally not considered, but just look at how many links there are on any Wikipedia page.
The Swedens have their own equivalent on susning.nu which has a feature I really like: hyperlinks aren't underlined. Reading on Wikipedia sometimes gets slowed down because of all the tempting links.
Wikipedia has a Swedish version too which claims to contain over 20,000 articles. (I might be wrong but Susning.nu seems much faster)
This is what Internet is all about!