inherent is a quality of something that can not be removed... A flashlight is inherently a tool used for seeing and produces light (or is meant to). Essential is a need that is important. It is essential that if you go down in the cellar, that you bring a flashlight to see.

check these two sentences out 1 Even in small companies, computers are an essential tool. essential meaning important, it needs to exist 2 Violence is inherent in our society. inherent means it exist, it's there. it doesn't need to be there and people may not want it to be there, but it's there. I think if we just look at the meanings of the two, esp their chinese meanings it seems a bit alike, but put it in sentences, the difference becomes easier to see :P