A regulated electronic trading service offered by the National Association of Securities Dealers that shows real-time quotes, last-sale prices and volume information for over-the-counter equity securities. Companies listed on this exchange are required to file current financial statements with the SEC or a banking or insurance regulator. There are no listing requirements, such as those found on the Nasdaq and New York Stock Exchange, for a company to start trading on the OTCBB.
Stocks that trade on the OTCBB, will have the suffix ".OB".
Taobiz explains Over-The-Counter Bulletin Board - OTCBB
It is important to note that companies listed on the OTCBB are not a part of the Nasdaq Exchange. The truth is, OTCBB stocks are not especially large or stable and are considered very risky. As a result, very few OTCBB stocks are successful in making the jump from this market to the Nasdaq or any other major exchange because they are unable to meet the listing requirements. Furthermore, because OTCBB stocks tend to trade infrequently, the bid-ask spread is larger.