I've never traded stock from a brokerage house, but I have taken some financial economics classes, so I'll give you some definitions.
The Ask price is the amount that it will cost you to buy the stock on the open market.
The Bid price is the amount that you will be able to sell your stock for on the open market.
The more liquid the market for the stock is the lower the difference will be.
The diffence between the bid and ask prices is called the spread.
This is how dealers make money off of the transaction. They make the spread.
Some stock markets like the NYSE has a person above the dealers called a Specialist. Each stock owned by a Specialist. The specialists have more information about the market than anyone else because they can see the market demand and supply first. They can choose to reveal this information or keep it secret. For the right to the info though they have to perform the responsibility of creating a market. The specialist owns large number or shares and are required to buy or sell as necessarily to keep the market liquid even if they have to lose money temporarily.
