Many job search committees for teaching, graduate school, international or research positions request a CV to get a fuller picture of your academic experiences, accomplishments and interests than a resume can provide.
A resume lists your education, experience and skills. Your CV allows you to go beyond listing your relevant experiences and accomplishments; you can also convey the substance of those experiences and accomplishments.
Unlike a resume, which is usually about one page long, CVs vary in length, from about two to five pages, depending on the applicant's relevant experiences.