The essence core (丹田) actually literally translates into “cinnabar/red field”. It is sometimes translated as “elixir field”. It looks more like a concentrated ball so sometimes it will be referred to as “inner field” on this site. The Chinese name is dantian.

There are actually three of these (an upper, lower, mid). Most novels only focus on the lower one but drop the word “lower” from the name. The lower one is usually what makes or breaks a martial artist. You have to establish the lower inner field first to be able to train in martial arts. If your lower inner field is destroyed, your life as a martial artist has also been destroyed. The lower one is located roughly 2-3 inches / 6 cm below the navel. The upper one is located in your brain. The mid one is located close to your heart but in direct line on your spine with the other two.