The letter which is attached to a resume which you send to a company is known as covering letter. It plays a vital role in your job application process. There are different types of cover letters for different types of jobs. Some of popular Cover Letters Categories include:

1. Accounting: It is for accounts and finance related jobs.
2. Legal: It is for all sorts of Legal jobs.
3. Advertising: It is for promotion and advertising of a product or services.
4. Call Center: It is for call center related jobs.
5. Designing: It is for web or media designing related jobs.
6. Actor: It is basically for actors and acting related jobs.
7. Administrative: It is for administrative jobs.
8. Banking: It mainly covers investment and banking related job.
9. Construction: It mainly covers construction related job.
10. Engineering: It is for engineering related jobs.
11. Technical: It is for all kind of technical jobs.
12. Sales & Marketing: It mainly covers sales and marketing related job.

Above i have just pointed commonly used cover letters categories. One can also write this letter for resume, job, acceptance, rejection, salary increment, appraisal etc. The main purpose of writing a covering letter is to formally introduce you. You can also personalize the presentation of your resume. Items which are not addressed in your resume can be focused in this letter. It will surely help to facilitate a meeting between you and the employer. Information on how to write this type of letter can be easily found on internet. There are lots of good cover letter templates to choose from. Here are few cover letter tips:

Never use generic letters. It should not be hand written. Try to finish it up in single page. Don't use more than one sheet of A4 size page. One should not forget to check that he/she have included everything in his/her letter before posting.

More information on letters can be found at Sample Letters http://www.sampleletters.in/.