(noun)
the most important quality, aspect, or element of something or someone, especially one that is distinctive to the thing/person;
e.g. This process is the essence of effective governance.
(noun)
someone or something that exhibits some quality in abundance, as if they are the concentrated form of the quality;
e.g. He is the essence of kindness and generosity.
(noun)
a substance that is extracted or derived from a plant or some other source and that possesses the special properties of the source, which is subsequently used for its scent, flavor, or therapeutic value;
e.g. This cake uses vanilla essence as its primary flavoring agent.