To get a jump start on the year, here are some basic terms you should know.
Manorialism
Feudalism
Titles of Nobility (particularly in England)
Each of the above will have other terms associated with them. For example, to understand Manorialism you need to understand what a Lord is and what a Manor is. For Feudalism, you need to understand what Lord, Vassal, Fief, Fealty, Serf, etc. are. So be sure to familiarize yourself with all the associated terms too.
You can use any sites you wish, but Wikipedia isn't always the best source. Be sure to check at least three different webpages for each one. (That's what historians do, we plunder a lot!) Here's a good website to start you off....
http://www.medieval-life-and-times.info/medieval-england/manorialism.htm
Enjoy!
Mr. Preece