What is an essential job?

A very important job.

Explanation:

Essential means very important, and must have. So an essential job is a job that is very much needed. A couple good examples are docters, police, firefighters, etc.

Essential job functions are the fundamental duties of a position: the things a person holding the job absolutely must be able to do. Essential job functions are used to determine the rights of an employee with a disability under the Americans with Disabilities Act (ADA). An employee who can't perform the essential job functions, even with a reasonable accommodation, isn't considered qualified for the job and isn't protected from discrimination.