In many cases, your resume is the first document a hiring manager will look at when reviewing your application, and therefore is a true “first impression.” Accordingly, it’s important to put time and effort into developing and maintaining an updated, accurate resume.
In the United States, a CV is almost exclusively limited to professions in academia, science and medicine. In the case of academia, the main focus of the CV should be to identify yourself as a scholar. The added length, should be filled with proof of your skills as a teacher, scholar, and your knowledge of education. A CV should be thought of as a living document, and it will change frequently based on the updates in your education and career.