Bio-Char aka Activated Carbon
Bio Char is basically activated carbon. It is created when you take wood and burn it in the absence of oxygen. When this process is done it looks like plain charcoal. Activated carbon is used for taking undesirable compounds out of water and is popular for water filters in the home.
Bio-Char or activated carbon has many microscopic holes that grab and hold compounds as it has a tremendous surface area. Biochar provides organic carbon compounds and minerals to soil. When BioChar is soaked in something like compost "tea" it will absorb whatever is in the "tea".
This Bio-Char can be used in the garden to provide minerals and organic compounds into the soil. Some in the urban farming or market gardening industry claim Bio Char is amazing for a soil amendment.