Whenever anyone starts off by saying that English isn't their native language, they then seem to write with better spelling/grammar than most native English speakers! Maybe the terms are difficult because they're new maths concepts rather than foreign words? I don't relate terms like differentiation, cross product or determinant to anything else in real life - their only meaning is mathematical to me.
Anyway, basic algebra, trigonometry, vectors and matrices are all good things to know about. Calculus may also be relevant, depending on what you choose to do. I find Wikipedia is a good first reference for maths concepts I'm not familiar with.
I think the main reason is most non-native learn the grammar first before they form any sentence while native usually start forming sentences before they even know about the grammar.
