Activated charcoal and activated carbon differ primarily in their surface area and reactivity. Activated charcoal has a significantly higher surface area, which can reach up to 2 square kilometers per gram, making it highly effective for filtration and pyrotechnics. This increased surface area allows for more reactive sites, enhancing its ability to absorb chemicals and impurities compared to regular coal-carbon, which contains many impurities and is denser. While activated carbon is chemically treated to maximize its surface area and reactivity, once it has been fully utilized, its effectiveness may diminish, approaching that of coal-carbon.