underlined stuff are links
Fallout 3 Wiki
Things to know:
+ Post apocalyptic Conditions (which is kind of obvious)
+
Creatures: radroach, ghouls, supermutants, feral ghouls, Brahmin
+
Factions: Wastelander (humans living in the wasteland), Vaultdewller (humans who hid in government underground shelters), Raiders, Brotherhood of Steel
+ History: All countries launched Nukes on each other and the current world is the result
MAYBE
skills But only to give you an idea of some abilities available. Ignore all the extra information on the page. Only the first 2 columns are important from the skills list.
This is what I think is the need to know. A few more minor things may pop up but that's circumstantial. Regular wastelanders will know these things. =) If you have any questions feel free to ask. I know what I'm throwing at you can feel overwhelming. But don't worry Fallout is a fairly typical post-apocalyptic world. I promise.