What's the difference between CV and Resume ?

A C.V. would list every important thing you've ever done. A resume lists the most pertinent aspects of your preparation for a particular job.  I know people with CVs well over 20 pages long, but a resume only a page or two.

One friend lists every time he has ever been interviewed for a digital show, or on radio or TV or for a newspaper article, plus every time he has given a speech or lectured (including webinars), and everything he has ever published, including web pages, magazine articles, blogs, etc.  All of that would be summarized in two or three sentences of a resume.

In the US a CV is only used for research or academic positions, where the details of what you did are important before talking to you.

A resume is a brief overview that highlights what makes you special and used for most employment in the US.

I don't know if a CV in other countries is more like a resume or what American's use a CV for.

The same ! a CV is the British version of an American Resume.

Both detail personal details, education and employment history.

They are the same thing, Americans usually call it a resume, Brits call it a CV. I had a Microsoft Works template years ago called Resume/CV.

The difference between a CV and a resume lies in the length, layout, and purpose of these documents. CVs have no length limit; resumes are typically one to two pages long. A CV details the whole course of the candidate's academic career; a resume summarises skills and work experience

A CV is usually prepared by academic people.  It will emphasize research, books, papers, etc. that the individual has done.