Several thousand companies have chosen to be listed on NASDAQ, which is an all-electronic stock exchange. In order for it to work all-electronically, an elaborate system of computers must work together synchronously. This system has three separate elements: the interface, the "matching engine," and the stock quote server.
The first element is the place where broker/dealers and market manufacturers access the system. The computer that connects buyers and sellers when their computer-recorded prices match is the matching engine. NASDAQ's quote server information is made up of the data coming from the matching engine when trades are actually transacted.
The prices of stocks fluctuate constantly. People want to know real-time price information, though, and so do broker/dealers as well as news services. The system of computers that runs NASDAQ, that records and regurgitates all the data, operates in real-time by analyzing what's happening in the matching engine element and then posting that data.
In very simple form, here's how it works. NASDAQ's broker/dealers electronically receive buy and sell orders from their clients. These trades are fed into the NASDAQ system through individual computers, one per broker/dealer. These trades are routed to the matching engine, a single computer. This is where the actual trading (buying and selling) occurs. The computer matches all its sell orders to the closest-matching buy orders and returns that information to the broker/dealers. An exact match will be transacted immediately and that data sent to the broker/dealer, as well as to the quote servers, as that is the most recent, up-to-the-minute quote on that particular stock.
Any information re. a stock quote, whether real-time or delayed, is considered stock quote data, but delayed stock quotes are obviously of less value to traders wishing to buy or sell right now than real-time quotes. On the other hand, someone who is tracking a stock, or charting it, looking for trends, doesn't need a minute-by-minute data feed.
Data concerning stock quotes, historical, delayed or real-time, can be obtained from a wide variety of Websites. Some is available free; the data that isn't comes packaged in a wide array of prices, most of them wrapped around a monthly "membership." Of course, some of this same data is also available at the other end of a telephone - if you call a brokerage. RSS, streaming quotes and stock charts all provide stock quotes data.