The term "cover letter" is used generically to refer to a letter accompanying, and in some manner, explaining another document. One very common type of cover letter is one job applicants send to accompany a resume. A crucial point about a cover letter, and one important in making a good impression on employers, is that it does not merely recapitulate the information in the accompanying resume or other documents, but instead explain the purpose for which the information was sent, and guides the reader in processing the accompanying documents, often by adding some form of "spin" or persuasive slant.
a cover letter is that letter which written before a resume. cover letter is used generally to refer to a letter attached here with it andit also explains the another document i.e.resume. it makes a good impression on employer coz before reading resume an employer reads your cover letter... it is a first impression that you made on employers mind.....as you all know first impression is the last impression.