A cover letter is a professional business letter that provides a potential employer with important information about you and your background. The objective is to demonstrate why you are a perfect match for the position you are applying for and why the employer should interview you.
A cover letter emphasizes your skills and abilities and provides an opportunity for you to highlight one or two of your professional accomplishments. The cover letter is meant to be concise and not restate information presented in your resume. Your cover letter must always be an "original" letter and never be a form letter. When sending a resume to an employer, always include a cover letter.