In essence, buying a stock is buying a portion of a business. A really really small portion. If you were to buy stock in Disney, it would be like going to Disneyland and finding a rock- thats your portion (not literally, but you get the picture).
Why should I buy stocks?
To make money... you hope at least.
Think of stock prices like gas prices. They are fickle- they go up and down like crazy! Your goal is to buy low (think buying something on sale) then sell high (when your stocks are worth the most amount of money).
In addition, some companies offer dividends (aka they pay you a small amount of money on a regular basis so that you will buy there stocks and keep your money invested in their company). Personally, I love dividends!
Where can I buy stocks?
Generally, most banks have an investment section of their company and their are many financial advising firms out there too. The problem with both of these options is that most people who work at these places are commission based employees- meaning they make most of (if not all of) their money by selling- NOT advising.
If you decide that you would just rather buy stock on your own then have to deal with sales people then you are in luck! Their are a few online legit places to buy stock. My favorite is Charles Schwab.
Thats all for now. And don't worry, it only gets more complicated ;)