What is a letter of recommendation?

A letter written by someone who knows your work habits that explains why you'd be a good employee

a brief document written by someone who is not a family member, but who knows you well and explains why you would make a good employee.

Auditor's letter addressed to the client. It contains the public accountant's conclusions regarding the company's accounting policies and procedures, internal controls, and operating policies. An evaluation is made of the present system, pointing out problem areas.