A job description is written for internal use and sets out the role in full. The advert is a shorter, persuasive version for people outside the organisation. It typically leads with what the job involves day to day, then covers pay, location, working pattern and the essential requirements, and ends with a clear way to apply. Plain job titles and stated salary ranges make roles easier to find and judge.
The advert shapes who applies, so it affects the quality of the applicant pool before any screening begins. Long wish lists can put off capable people who do not tick every box, while vague wording invites applications from people who are not a fit. Keeping requirements short, stating must-haves clearly and avoiding exclusionary language helps attract a broad, relevant pool.