Copal is a resin. Resins are solidified pieces of plant sap, and they are very fragrant when burned. Copal comes from various species of the Bursera tree, in Mexico and South America. Copal (like most resins) are burned or smoldered as incense during ritual. But it needs to be burned on charcoal blocks because it's not flammable on it's own. Don't overdo it! Resins can produce a lot of smoke, so only burn a small amount at a time. Copal is absolutely wonderful :3