Common Stock:  
Usually the majority type of all shares outstanding in a company. These are units of ownership that include voting rights at shareholder meetings. Of course, you have to have a large amount of stock before your vote can carry enough weight to sway decisions. Otherwise, most shareholders' votes are considered symbolic to indicate their agreement or displeasure with corporate management. Common stock is usually traded under the main symbol for a company's stock. For example, Ford Motor Company is traded under symbol, "F."

Preferred Stock:  
This class of stock typically does not include voting rights, but can carry other benefits that its shareholders can enjoy BEFORE common stock shareholders. They may be entitled to receive higher dividends, or priority payment of dividends, versus holders of the common stock. "Convertible Preferred Stock" is preferred stock that has a built-in option that shareholders have the right to "convert" their preferred shares into a fixed number of common stock, usually by or after a pre-determined date set by the company. Preferred stock is traded under a symbol that is different than the common stock. For example, the preferred shares of Ford Motor Company trade under the symbol, "F-PS."

A Stock "Bull":  
Someone who is known as a bull on a stock is "optimistic" or positive on the stock.  If they are "bullish," they believe the stock will go up in price.  "Bulls" also often promote the stock through newspaper articles, TV shows and website articles.  Be careful believing what these people are saying. Just as with bears, you need to find out if they are bullish, predicting the stock will go up (and trying to push it up), because they hold a significant amount of shares of that stock.

A Stock "Bear":  
If some is a "Bear" toward a stock, they are "pessimistic" or very negative about the future price of stock, and predict that it will go down.  Exactly the opposite of a "Bull"...they often "knock down" a stock price, pushing their opinion that the stock will go down in price.   Be careful believing what these people are saying. Just as with bulls, you need to find out if they are bearish, predicting the stock will go down (and trying to knock it down), because they hold a significant amount of shares of that stock but, in their case, they made hold these stocks "short" where they are betting that the stock price will go down, not up.  Learn more about Short Selling stock here >