A CV (curriculum vitae) is different from a cover letter in that a cover letter is more concise and a CV is fairly detailed. While a CV includes detailed information about a person's educational background and work experience, a cover letter is a more concise document expressing interest in the job being applied to.
edit Differences between a CV and Cover Letter
A cover letter is an introduction to yourself with regard to the job opening you are applying for. Cover letters are generally one page at most in length, divided into a header, introduction, body, and closing.
Curriculum Vitae may include a cover letter along with other details which are important when applying for international jobs, fellowships, grants, research, scientific and academic positions. The CV is used to screen applicants, often followed by an interview, when seeking employment.
A cover letter includes general details about a person like name, contact information, educational and professional qualification, work experience and career goal or what a person is looking for in terms of a job profile. A cover letter should not be confused with a resume as it does not include all the details of a resume. The cover letter should have enough details so that it complements the Curriculum Vitae and also interests the person reading it.