A cover letter contains an explanation of or additional information about an accompanying communication, such as a resume. It is sometimes called an application letter or letter of inquiry, whether it is sent in response to a job opening or mailed to a company for which you would like to work.
Employers receive hundreds of letters and resumes for each advertised position vacancy.
Your letter, therefore, will have to be well written and designed to attract attention in a positive way in order to receive a favorable response. Your cover letter should communicate something personal about yourself along with information that is specific for the division, organization or company to which the letter is being sent. This lets the reader know that you have spent some time researching the organization and writing a personal letter. Form letters elicit a negative reaction, if not a toss in the trash can. To receive a positive response, it is imperative that you research every company to which you apply in order to give knowledgeable and specific reasons for your interest in that company and how you can meet their needs through your qualifications, experiences and personal qualities.