Paid-in Capital represents the capital raised by an entity from selling part of its equity. It always includes common stock and may incorporate preferred stock and additional paid-in capital.
Common Stock represents the basic ownership of an entity. Holders of common stocks have a voting right in controlling the board of directors of a company. However, in case of insolvency (i.e., bankruptcy), common stockholders will be paid back after creditors and preferred stockholders. Common stock is equivalent to par value times number of common stock.
Preferred Stock is an ownership interest with specific preferences to common stock. For instance, preferred stockholders usually have a priority claim to dividends and are paid first in case of insolvency.
However, they do not have voting rights. Preferred stock is equal to par value times the number of preferred stock.
Additional Paid-in Capital reflects the excess of the amount received from the sale of preferred or common stock over par value.
Retained Earnings is the amount of net income that is left over after dividends to the stockholders, partners, or owners have been paid.