When employers are advertising job vacancies, they will produce a job description (an outline of the job, including a summary of the main tasks and responsibilities) and a person specification (the type of person they wish to attract, including essential and desirable criteria). These are available for each job on NHS Jobs. Job vacancies are usually filled through open competition, so you need to ensure that you read the job description and person specification fully, before making your application. In order to be short listed (invited for interview) for a position, candidates must meet at least all the essential criteria outlined in the person specification. More general information on job descriptions and person specifications can be found on NHS Jobs.