Many people believe that a CV and a resume are the same document but that is far from accurate. Back in the good old days, which means in the last century, a CV (which stands for curriculum vita or life book) was used by all white collar professionals when applying for a job. Slowly, many professions went to a shorter form and called it a resume. At the end of the nineties, most professions were using a resume for job search with only academics, medicine, scientific research, and attorneys still using the CV format. Seven years into the new century, and even that is now starting to change in the United States.
So what is the difference between the two documents? Where do I start? Let's consider geographies first. In the United States and Canada, a resume is used 99.9% of the time for job search, even by those in the professions mentioned specifically above. In Europe and other countries, a CV is still being used for the most part but the resume is gaining ground in western countries such as the United Kingdom and Australia. Many job seekers who are not in the US but are seeking employment here do not realize that a CV is not appropriate for a US job search and are hurting their job searches by using one.
The next difference between the two documents is the type of information included in each. In a CV, it is common to list personal information such as date of birth, marital status, children, health details, etc. CVs often include a photograph of the job seeker. All of this directly violates US hiring laws and can cause employers to shy away from the candidate out of fear of a lawsuit for hiring discrimination. A resume should never include personal information or a picture.
CVs are very long documents, often stretching to six or eight pages. The term life book applies because everything, whether relevant to the current job search or not, is included in a CV. Education details, publications, articles, speeches, presentations, detailed job histories, references - all are commonly seen on a CV. On a resume, the information is kept focused on the goal. The award of Eagle Scout would be listed on a CV but not on a resume.
CVs are written in a very vanilla language. They are meant to be life histories rather than a marketing document. A resume is written to sell the attributes of the job seeker that qualify him/her for a position. Phrases are shorter, written with stronger language, and a strategy is imposed to position the job seeker as THE best candidate for the job.
Employers in the US expect a resume from job seekers. The resume and cover letter combination are written and designed to not only present experience and background but present it in a way that markets the job seeker well. A CV is a listing of events and experience without consideration for positioning. It's analogous the comparison between an encyclopedia and a marketing brochure. The brochure is designed to sell while the encyclopedia is designed to inform.