What do you want to know?
The 4 letters you see next to the quotes are the trading firm or ECN (ie. INCA = Instinet, SSMB = Salomon Brothers, GSCO = Goldman Sachs ,etc).
You also have a bid and ask price that those cos are looking to pay or get and a share amount.
These things might not seem like alot of info but it is actually very helpful in determining what a stock might or is doing. For example, investment banks don't usually like to be an active market maker in stocks because they just don't make any money doing it these days. If a trader sees that MLCO (Merrill) is actively trading in a stock and always near the top of the list, he can assume that they have a big order on the desk or that they may be accumulating or selling because they expect something to happen.
If you want to know more, you can PM me.
I've worked at a hedge fund for 4 years and at an investment bank for 4 also.