Hi there jumpoff!
I've found a couple of really good resources which cover Mauritania.
The best place to start is the country study of Mauritania produced by
the Federal Research Division for the Library of Congress. It has
enough information to fill a book, but the best place for you to start
would be the Introduction section - which suits your length
The Lonely Planet guidebook series has put together some good, concise
information on Mauritania, available here:
Another excellent and even shorter overview of Mauritania can be found
at Infoplease.com, a good resource for questions such as these:
Wikipedia, the free internet encyclopaedia, also has some brief and
well written information Mauritania's history, economy, politics and
so on. You can find this here:
Finally, the best resource to turn to on the internet for country
information is the CIA World Factbook, updated every year and made
freely available to all. You can see their entry for Mauritania here -
it is more than a brief overview, but I'm confident you'll find some
good and useful information here.
I hope this helps! If anything's unclear, or needs elaboration, or if
the links do not appear to function, please don't hesitate to request
clarification before rating this answer.
Thanks, and good luck!
Mauritania facts figures