Charcoal is made by burning wood and other combustible materials in an oxygen-starved environment. The process yields a product that creates less smoke, puts off more heat in relation to its volume, and burns at a steadier temperature than regular wood.

Charcoal comes in two basic forms, lump and briquette. Lump, or hardwood charcoal is made from lumber scraps and other pieces of hardwood. It burns hotter, cleaner and more quickly than briquettes.

Briquettes are made from charcoal dust that's been bound with starch and often additives like fuel to help it light more easily -- good for convenience but not so good for flavor.

Reference: What does it mean to grill? (Cookthink)
Reference: Why do I need to soak wooden skewers? (Cookthink)