Pink Sheets refer to a decentralized over-the-counter (OTC) market for trading stocks of companies that do not meet the stringent listing requirements of major stock exchanges like the New York Stock Exchange (NYSE) or NASDAQ. This marketplace is named after the pink-colored sheets of paper on which stock quotes and trading information for these companies were historically published, though today, it's primarily an electronic trading platform.

Companies trading on the Pink Sheets are often smaller, less established, or international firms that may not have the financial strength or regulatory compliance necessary to list on major exchanges. As a result, Pink Sheets are sometimes associated with riskier investments.

Unlike major exchanges where trading is highly regulated, Pink Sheets trading can be less transparent, and the stocks are subject to fewer regulatory requirements. This can make it challenging for investors to access reliable and up-to-date information about these companies. Due diligence and research are especially crucial when considering investments in Pink Sheets stocks.

Pink Sheets stocks are designated with different tiers based on the level of information available and the companies' compliance with reporting requirements. The tiers range from "Current Information" for companies that provide regular financial disclosures to "Caveat Emptor" for stocks with significant concerns or a lack of information.

Investors interested in Pink Sheets stocks should exercise caution, conduct thorough research, and consider the potential risks associated with these investments due to the reduced regulation and reporting requirements compared to stocks listed on major exchanges.