How does an Air-Thru stock work?

How does the buy/sell mechanism of the stock market work?

• The prize at which an stock is at any given time is the prize at which the lowest transaction was made, and you can buy of that stock at that prize at that given moment, and to buy a stock there has to be someone who wants to sell it, the opposite is true when you sell a stock...But how can you sell a stock instantaneously?? there can't be someone who wants to buy that amount at the exact same time, and why would that person want to buy it at the market prize, i mean, there has to be a sort of negociation process or something..plz explain me how it works.

• Answer:

  Generally there are bid and ask prices, with a small spread between them. Someone presents a price and another decides whether to accept it. If you want to buy something immediately you will need to accept an ask price that someone has already presented. If you want to sell something immediately you will need to accept a bid price that someone has presented. The small difference between the two is the price you pay for securing an immediate transaction rather than waiting for the price that you want. The market price is just the last price that was paid, so it could have either been a bid or an ask.