Options Clearing Corporation
Options Clearing Corporation (also called "OCC") is a United States clearing house based in Chicago.  Clearing houses are used to help traders, and they make sure each trade is correctly made, or "cleared". The OCC does this "clearing" with stocks, stock options, and many things that are very much like options (called equity derivatives).  "Clearing" for stocks is very much like clearing a bank check.  The OCC provides this service to at least 14 exchanges, where stocks, options, and contracts to buy or sell copper, gold, grain, oil, and other needed supplies.  They also provide services for people and companies that need to borrow stocks.  When someone borrows a stock, they have to pay OCC some money every day.  This is the same as people who pay a bank for a loan of money.