It’s wood that has been charred, at a constant temperature for a period of time just below its combustion temperature. When it comes out it has a special characteristic that makes it great as an amendment to soil. Biochar has a whole bunch of tiny spaces inside it to hold: moisture, nutrients, enzymes, lots of cool stuff that replicates over time.

So when you place it in your soil it can benefit your crops for many years to come. Not all biochar is the same if it’s not prepared the right way tho. Not an expert, just took a class once. The place I went was in NC. Very neat ancient technology . Not sure if helpful but try this https://biochar-us.org/welcome-biochar-learning-center