Charcoal is the lightweight black carbon and ash residue produced by removing water and other volatile constituents from animal and vegetation substances.Charcoal is usually produced by slow pyrolysis — the heating of wood or other substances in the absence of oxygen (see char and biochar)., it is used in water filters, gas masks and antigastric tablets, capsule or powder for people suffering from indigestion. Wood charcoal is also used as a decolourizing agent as it can adsorb colouring matter.