A cover letter is an integral part of a job application that can unveil you as a serious job candidate. Many job seekers make the dire mistake of submitting their job application without a cover letter attached. Since the cover letter is often the first thing a potential employer sees, it should stand out amongst the sea of applications. A resume alone provides limited value to an employer if he or she isn't aware of what type of work you'd like to do. The cover letter tells the employer what position you are seeking and how you're qualified for the desired position.What is a Cover Letter?As the most effective page of your application, the cover letter is a simple letter in which you formally introduce yourself to your potential employer. Upon opening your job application, this should be the first document seen. In your cover letter, you should discuss your desire to become part of the company and provide the potential employer with a formal invitation to review your resume further. Your cover letter acts as a "bridge" to the rest of your application, complementing one another.What to Include in a Cover LetterIn general, cover letters should be three to four paragraphs in length, with each paragraph containing three to four sentences. The first paragraph should mark a formal introduction that includes information on where you learned about the position. Did you know someone personally connected with the company? Or perhaps you're responding to an advertisement in your local newspaper? Use any personal connections that you have to the business to your advantage by mentioning it in the introduction.In the second paragraph, focus the content on your credentials. Use this area to discuss why you deserve to be given a job. Write about your achievements and tell your potential employer what you could do for their company. A third paragraph can be added if needed for this information. In the final paragraph, try and persuade the employer to look at your resume. Always finish by thanking your potential employer and stating that you're looking forward to being contacted for an interview.