Cover letters are generally used along with a resume, business letter or work assignment. A cover letter is a very important piece to any document that it is tied to. The purpose of a cover letter is not to provide details or even answer any questions. The point is to grab the attention of the reader. Once you gain their attention with a strong cover letter, then you can convince them with the details in the document behind it. The attention of your reader can easily be obtained by focusing on their needs, or exactly what they are looking for.