Carbon is above us, below us, around us, and in us. It cycles back and forth between the air and Earth's surface (soil and water) with the help of every living thing, including humans. As carbon goes through this cycle, some carbon stays put for a time while some is on the move. The carbon that stays put in soil is sequestered there. 

In a balanced cycle, plants make carbon-based sugars through photosynthesis, and move it into the ground at an equal or faster rate than carbon is being released from those soils. Healthy soil, and undisturbed plant-covered soil, is key to this balance because it can sequester more carbon from plant roots and dead decomposing organisms.