A cover letter and a CV are different documents. A cover letter is a short (1 page) letter that is paired with a resume to elaborate on your qualifications and introduce yourself to an employer.
Meanwhile, a CV (curriculum vitae) is a lengthy document (sometimes 2+ pages in length) that highlights your academic career, work history, and achievements. A CV is used instead of a resume to apply for positions in academia or research.
If a job application requests a CV, don’t just send your cover letter. Depending on the context, you’ll need to write a job-seeking CV or an academic CV. If applying for jobs abroad, be sure you understand local CV-writing standards.