What an introduction is
What it's for
The introduction serves as a hook; it's where you pitch your article, be it your settlement page or your character page. If you're a regular browser of wikipedia, you know what it is, it's that top portion of the page where they say that Albert Einstein was a German-born theoretical physicist, etc, etc. It's kind of like a résumé. By reading the introduction, you're setting a mood for the rest of the article: you're introducing something and inviting people to read on.
How to write one
As this is where you get a general feel for a settlement or character, you might choose to set a certain tone for it which may result in it being less factual and more of a quick impression and summary.
On the other hand, you can keep it purely factual. A good example would have to be the introduction on Albert Einstein's page. If it's intended to be factual, it's best to write their birthdate, their birth place and a quick introduction of what they've done for a living and how they died (if appropriate).