The use of essential and vital in english language

First, essential is used for something very important and completely necessary, because without that thing something cannot exist.
Vital, is used for something important but not as necessary as essential.
These words have the same meaning but there can be a slight difference in the tone. Essential is used to state a fact or opinion with authority. Vital is often used when there is some anxiety felt about something, or a need to persuade somebody that a fact or opinion is true, right or important. Vital is not often used in negative statements.