Meaning of “essential” - Learner’s Dictionary

essential

adjective uk us /ɪˈsenʃəl/
NECESSARY

B1 very important and necessary:

Computers are an essential part of our lives.
Fibre is essential for a healthy digestive system.
[ + to do sth ] It is essential to arrive early for the show.
[ + (that) ] It is absolutely essential that she gets this message.
BASIC

the most basic and important:

There's one essential point I think you've forgotten.

(Definition of “essential” from the Cambridge Learner’s Dictionary © Cambridge University Press)