Be careful about the terminology from "les cousins d'Amériques", as usual there is some slight differences :) (first and foremost french people call it "course d'orientation" while in Quebec it is "orientering" with one 'e')
The wikipedia page in french should give basic terminology, including different types of race:
http://fr.wikipedia.org/wiki/Course_d%27orientatio...
I can send you a pdf which should provide a good summary of technical terms (it is technical document for training and learning purpose)
For terrain type, it's a bit more difficult, so ask me by mail which kind do you think of.