Type of shares are generally split into two: common/ordinary (depending on the jurisdiction) and preferred. The former are granted to founders and employees (most commonly as options with a right to purchase common/ordinary shares). The latter are generally issued to investors and include special rights such as liquidation preference, anti-dilution protection, etc. Preferred shares reflect the fact that the holder (investor) has paid a premium in consideration for issuance of such shares. Don't forget to consult with a lawyer.