I think most of the answers so far are speaking about the use of the terms in the US. 

In the UK, it's always called a CV. Résumé would be understood, but it's a US English term. The assertion above that CVs are some monstrosity of "an untold number of pages" is just not true here. Standard CVs are almost ubiquitously two pages long, although academic ones may indeed be longer, and ones in other particular fields may be shorter.