There are two types of charcoal. Briquettes, and lump.
Briquettes are made from wood scrap, fillers, and binders. Think Kingsford, or Matchlite or the alike.
Lump charcoal is made from solid chunks of wood. No binders, no fillers, just wood. Lump has much less residue due to the lack of fillers.
Charcoal is made by burning wood in a low oxygen environment. The water, and much of the volatile organic compounds are driven off. What is left is a wood fuel in a handy to use form.
If you look on this page you will see some pictures of lump charcoal, and will be able to recognize pieces of wood.
That page is from lump charcoal database where you can read reviews of various brands of lump.
Me I use lump in my q. Better flavor, and burns hotter.