Resume is generally a description of your personal basic situation, this is your resume, but the cover letter should highlight whether your ability is suitable for this job; A cover letter looks more intimate, not as blunt as a resume. Generally speaking, a cover letter is to better impress HR through your language and let him know more about you from the perspective of human nature. General foreign companies need more cover letters. That's all I know. I wish you a successful interview and find a job that suits you!