OTC stocks are frequently those of smaller companies that are unable to meet the exchange listing standards of regular exchanges. However, other types of securities are traded here as well. Listed stocks are those that trade on exchanges, whereas unlisted stocks are those that trade over the counter.

OTC Markets Group's electronic matching platforms can be used to conduct trade transactions:
The Pink Open Market, OTCQX, and OTCQB (also referred to as OTC Pink or "Pink Sheets").

Each of these platforms contains a progressively lower (and thus riskier) layer of equities from various corporations. Stocks in the top tier of the OTCQX must meet a number of eligibility requirements and contain a large number of international ADRs. The OTC Pink tier is the least stringent in terms of listing standards and quality control.

OTC (Over-the-Counter) stocks refer to securities that are not listed on formal exchanges such as the New York Stock Exchange (NYSE) or NASDAQ. Instead, they are traded directly between parties, typically through electronic networks or broker-dealers. OTC stocks often include smaller companies that do not meet the listing requirements of major exchanges or are unable or unwilling to comply with the regulatory obligations associated with exchange listing. These stocks are also known as "unlisted stocks" or "pink sheet stocks." Trading OTC stocks can carry higher risks due to lower liquidity, limited public information, and potential for price volatility. Investors interested in OTC stocks should conduct thorough research and exercise caution, as these securities may be more susceptible to manipulation and fraudulent schemes compared to those listed on regulated exchanges.