[lookout123]

The first thing: If you own STOCK, it means you literally own a portion of that company. you may have a physical certificate, but that is being phased out in favor of electronic registration. Stock is generally bought and sold on the open market. Transactions are generally completed through one of the exchanges, or clearing houses. (New York Stock Exchange, American Stock Exchange, etc.)

The little numbers change all the time, because thousands and sometimes millions of shares of a specific stock are traded in a number of different transactions. each transactions may have been for a different purchase price that can change based on supply/demand as influenced by market conditions.