Definition - What does Earthing mean?
In relation to marijuana, earthing is covering the entire root system of the plant underneath soil. The roots of the plant are not exposed to harmful ultraviolet rays and are better able to absorb water and nutrients through the soil. The benefits of earthing are also transferred to those who partake of ganja that is earthed, and if partaking while barefooted on soft soil while partaking, will find the most benefit. The idea of a plant whose roots are not surrounded with either soil or soil-like medium is known to many as hydroponically grown.
MaximumYield explains Earthing
The only problem with plants that are grown hydroponically is that they are not earthed, meaning literally that their roots are not covered and surrounded by earth. There are many benefits to earthing, including the microbes that live in the soil and provide nutrients and drainage for the roots. There is less intensive care used when a plant is earthed, and it is the most natural way to grow.