What is the Dantian丹田? Let’s look at the Chinese character for Dan 丹, it is like a cauldron. In ancient China Daoist would make medicine by putting a mixture of different herbs and other things in a cauldron. They would slowly heat this up and simmer it for hours or even days. By the end they were left with the essence of the herbs and they would make this into a pill or tablet. This pill is what we call Dan and even today there are some Chinese medicines which are still made this way. So Dan is the essence of the medicine, or the elements that make it up. In the past even emperors wanted these Dan as they believed they would make them live forever and so become immortal. When someone has all the power they want to keep it and live forever. Of course no one can live forever, but the Dan was still very useful for treating different diseases. In the western way, Dan is also equivalent to crystal. In all, it means Dan is the essence of Qi.
Tian 田 means field, the same as a famer works in, it also means area.
Dantian means the area for the essence of Qi. It is very important although we cannot physically find it by using surgery to look inside us, but we can feel it and this is how we know it.