Desirable qualification -
Desirable qualifications mean the requirements of training and experience desired but not necessary to qualify for a given class of positions in the classification plan.
This may be used to decide who to invite to interview if an organization has a high volume of applications.
Essential qualification -
Essential qualification means the qualification that is required for applying or for qualifying for a job as it is “essential” for the correct performance in the job. For example, graduation is an essential qualification needed to apply for some jobs like SSC/BANK/UPSC.