A curriculum vitae (CV) catalogs your working career (including accolades, presentations, publications, education, extracurriculars, etc.) in a chronological order with detail. I think about a résumé as a snapshot of the CV. Typically it’s less than a page and only contains highly relevant points which differentiate you from other applicants.
In either case, it’s important to have easy access to an updated copy of both for volunteering positions, job applications, and especially higher level education applications. I’ll provide some tips about keeping an updated CV knowing that the same tips apply in generating a résumé based on the position you’re seeking.
In general, I have a copy of a CV and a résumé on a cloud storage with word processing capabilities (ie, Google Drive or Office 365), so you can update these documents on-the-go. I focus on updating the CV and will regenerate a résumé based on the position I’m seeking.