U.S. stock exchange does not own any shares. Instead, it acts as an operator to provide a market connecting stock buyers with sellers. Stocks can be traded on several exchanges such as the New York Stock Exchange (NYSE) or the NASDAQ.
Over-The-Counter (OTC) refers to markets other than the organized exchanges described above. OTC markets are generally the venue list well sought after by small companies, many of which have fallen off to the OTC market because they were delisted. Two of the major OTC markets are:
Over-The-Counter Bulletin Board (OTCBB). OTCBB is an electronic community of market makers. Companies that are delisted from the Nasdaq often are often traded on OTCBB.
The second OTC market is referred as Pink Sheets, a listing service that doesn't require companies to register with the Securities and Exchange Commission (SEC). OTC liquidity is often minimal, and these companies are not required to submit 10Qs.