Stock charts show the price performance of a stock over time, and the letters represent what company you're viewing. Each company has a ticker symbol, which is a code used to find information and charts on that stock.
Each security listed on a stock exchange has a ticker symbol ranging from one to several letters. To search for a stock, input either the company name, or that ticker symbol, to bring up a stock chart. Given time, associating ticker symbols with the companies they belong to will become second nature.
Stocks listed on the New York Stock Exchange typically have one to three letters in their ticker symbols. For example, the ticker symbol of General Electric is GE, and the symbol for Walmart is WMT. (Some have four letters, like LinkedIn's "LNKD" -- but these are rare.)
A ticker symbol with four or five letters likely belongs to a company listed on the NASDAQ stock exchange. Microsoft is listed on the NASDAQ with the ticker symbol MSFT. Apple Inc., is also listed on the NASDAQ under the symbol AAPL. As of 2007, the Securities and Exchange Commission allowed three-letter symbols on the NASDAQ (though they're rare).
Additional letters are occasionally added to a ticker symbol, providing you with more information. The most common is when a company has issued multiple classes of shares. Varying share classes generally have different shareholder voting rights and stock prices. This is because the stocks were issued at different times or for different purposes. If a company has multiple classes of shares, they are labeled A and B. Warren Buffett's company, Berkshire Hathaway Inc., has class A and class B shares, with ticker symbols BRK-A and BRK-B, both listed on the NYSE.
There are stock exchanges all over the world, so to differentiate one country's stocks from another, a period and more letters are added after a stock's ticker symbol. SU.TO is Suncor Energy, listed on the Toronto Stock Exchange in Canada. Stocks on the London exchange have a ticker symbol followed by ".L". A ticker symbol followed by .PK is a "pink sheet" stock listed on the over-the counter market. This is a non-centralized marketplace, typically catering to very small or emerging companies, and penny stocks. Pink sheet stocks don't need to meet any eligibility requirements, as they would on a stock exchange such as NYSE or NASDAQ.
Cory Mitchell has been a writer since 2007. His articles have been published by "Stock and Commodities" magazine and Forbes Digital. He is a Chartered Market Technician and a member of the Market Technicians Association and the Canadian Society of Technical Analysts. Mitchell holds a Bachelor of Management in finance from the University of Lethbridge.