A cover letter is either sent with your CV in the posts or more commonly sent with an attached CV in an email to a prospective employer. A cover letter is your chance to have an effect on the employer and demonstrate your skills that related to the job you’re applying for.
The CV should ideally support the information in your cover letter, because the employer is likely to be looking through both documents to find relevant information. There are right ways and wrong ways to create a cover letter, and it’s not just a case of writing a long introduction about why you’re a really good employee.
Instead you should ideally prepare a cover letter with 3 to 4 skills that are listed in the job description, perhaps the most important skills, and it should be very specific to what you can offer. You shouldn’t just list general skills, and when you read back over your cover letter it should be authoritive, straightforward and accurate to your CV, If you can do this, you’re more likely to improve your chances of gaining a job.