What is an essential worker?

This is a venting piece basically. I work in a grocery store and I am tired of people thanking me for working but they are not willing to do anything to help the situation. My co workers get cussed at, they won't follow any signs or restrictions, and always want to try to tell me what I should do to "protect myself while standing way too close. It's a lot and I'm upset that it doesn't seem like its going to get better.