BioChar is pure carbon. It's very much like charcol, but all of the volatile materials are completely burned off. What's left behind is a very light structure of carbon.
This structure of carbon is very porus. 1 gram (an amount about the size of a pencil eraser), has over 9,000 square feet of surface area. Biochar is even electrically charged to attract all the right stuff to it.
Plants need Sunlight, water, nutrients, and micro organizms to thrive. BioChar assists by holding water, and nutrients for the plants. More importantly all the pores of BioChar are like apartment buildings for micro organizms. This gives a place for the micro organisms to grow and reproduce.
Put it in your ground!