Both stock exchanges and commodities exchanges involve traders buying and selling something -- a share of stock in one case, a commodity or commodities contract in the other. Likewise, these markets are made up of multiple entities that handle certain types of trading. For example, the NYSE and Nasdaq deal in stocks, and companies that sell shares must decide with which one to list their shares. The Chicago Board of Trade and Chicago Mercantile Exchange deal in futures, in one case grain and the other animals and their products.