OTC (over the counter) is the stock market version of "for sale by owner." It's a process by which stocks, bonds, and other financial
instruments are traded directly between two parties instead of on a public stock market, such as the New York Stock Exchange (NYSE) or Nasdaq. In other words, OTC is an alternative to a centralized exchange such as the New York Stock Exchange. Instead of going through the formal exchange, trades are done via a network of dealers or brokers on the open market.