What does that (cf) mean?

As the subject says, what does (cf) mean? It's probably something that gets passed me due to the language barrier; my native tongue is Swedish.

It is short for "confer," a Latin word meaning compare or consult. It means go look up this other thing and consider the two situations.

Also, I feel compelled to pedantically point out that Vincent uses cf. in places where he should really more properly be using q.v., an abbreviation which Zak Smith explains perfectly:

Q.V. stands for "quod vide", and I don't speak Latin, but I assume it means either "so, yeah, good luck finding that" or simply "go fuck yourself".