Why is it important that all positions in the organisation have position descriptions specifying key requirements of the role(s)?

Having a job description is very important for the job applicant to know about what the job consists of and what he will be doing as job. This will provide him/her to have a good understanding of the job and asks they are to perform as an individual. It will also provide them information on where they fit in the organisation and will help them avoid disputes and misunderstandings.