The primary purpose of any business is to create profit for its owners, and the dividend is the most important way the business fulfills this mission. When a company earns a profit, some of this money is typically reinvested in the business and called retained earnings, and some of it can be paid to its shareholders as a dividend. Paying dividends reduces the amount of cash available to the business, but the distribution of profit to the owners is, after all, the purpose of the business.
Some companies pay stock dividends rather than cash dividends, in which case shareholders receive additional stock shares.
 See also