Employers should only arrange a DBS check on a successful job applicant. They can withdraw your job offer if the results show anything that would make you unsuitable for the job.
If your employer applies for a check, the DBS will give your employer a certificate and you will also get a copy. This will list any offence(s) for which you have been cautioned or convicted. The list will show the dates of any offences and the punishment you were given.