To make black charcoal the wood is carbonized (partial burning with little air) at temperatures between 400 and 700 °C, then the kiln is sealed until the burning stops and the heat slowly dies away. You can now see the surface of the charcoal is black. Black charcoal is soft and retains the outer layer of the wood. It is also easy to ignite and burns hot enough that it was used as fuel for tea ceremony, and ordinary daily food cooking including industrial use during the former times.
Charcoals produced around the world are mostly soft black charcoal type.