I am turning 18, and wanted to know how the stock market work.
A company can issue "shares" that represent ownership in a portion of the company. For example, if a company has issued 1,000,000 shares and you own 1,000 of those shares, then you own 0.1% of the company. The word "stock" is another word for "shares".
A stock market (there are actually several) is a system that enables people to buy and sell these shares. Each stock market operates slightly differently, but in general this is how buying and selling works:
If you are selling, then you tell the market how many shares you want to sell and for what price. If someone else has told the market that they will buy shares for your price (or higher) then your shares are sold to that person. Otherwise, you have to wait until someone is willing to pay that price.
On the other side, if you want to buy shares, you tell the market how many shares you want and how much you will pay for them. If someone has told the market that they will sell for that price (or lower), you buy the shares from them, otherwise you have to wait until someone is willing to sell the shares at your price.
The reported price of a stock is simply the price of the stock in the last trade.