The text on the front page assumes people already know what is a wiki and what can it be used for. It states many things which are irrelevant if you don't know why would you want to use MediaWiki.
Topic on Template talk:Main page
Ping @AKlapper (WMF) just because.
I see a "What is a wiki?" link on the front page...
This post was hidden by AKlapper (WMF) (history)
what we can do with this page