Carbonate hardness is a measurement of amount of carbonates and bicarbonates in water . It relates to the 'buffering'property of water, which is how it keeps a stable environment for aquatic life.
Aquavascular KH Boost keeps the acid-base balance  in check. Additionally , it avoids abrupt pHshifts and sustains dissolved CO29ppm) in relation to pH.
For a planted tank , maintaining the KH between 3-6 dKH is desirable.