Common stock is, well, common. When people talk about stocks in general they are most likely referring to this type. In fact, the majority of stock issued is in this form. We basically went over features of common stock in the last section. Common shares represent ownership in a company and a claim (dividends) on a portion of profits. Investors get one vote per share to elect the board members, who oversee the major decisions made by management Over the long term, common stock, by means of capital growth, yields higher returns than almost every other investment. This higher return comes at a cost since common stocks entail the most risk. If a company goes bankrupt and liquidates, the common shareholders will not receive money until the creditors, bondholders, and preferred shareholders are paid.
Preferred stock represents some degree of ownership in a company but usually doesn't come with the same voting rights. (This may vary depending on the company.) With preferred shares investors are usually guaranteed a fixed dividend forever. This is different than common stock, which has variable dividends that are never guaranteed. Another advantage is that in the event of liquidation preferred shareholders are paid off before the common shareholder (but still after debt holders). Preferred stock may also be callable, meaning that the company has the option to purchase the shares from shareholders at anytime for any reason (usually for a premium).
Common and preferred are the two main forms of stock; however, it's also possible for companies to customize different classes of stock in any way they want. The most common reason for this is the company wanting the voting power to remain with a certain group; hence, different classes of shares are given different voting rights. For example, one class of shares would be held by a select group who are given ten votes per share while a second class would be issued to the majority of investors who are given one vote per share.
When there is more than one class of stock, the classes are traditionally designated as Class A and Class B. Berkshire Hathaway (ticker: BRK), the company of Warren Buffett (one of the greatest investors of all time), has two classes of stock. The different forms are represented by placing the letter behind the ticker symbol in a form like this: "BRKa, BRKb" or "BRK.A, BRK.B".