Which information does the body of a cover letter include

The cover letter of any official letter should include the main positive points of the candidate.

Explanation:

It is best to try to put everything that will make it hard for the company to not hire you. In other words, you are selling yourself as the best candidate for the job to them and making sure that you got your best options available. So, an applicant's cover letter should give compact details about one's qualifications, what position one is applying for, why s/he should be hired and why s/he is the best candidate for the job.