Dividend is a distribution of a company's profits to its shareholders. This distribution can be in the form of cash or shares.
Usually Cash Dividends are a percentage of the book value of shares. Some companies pay these every quarter and some pay only once a year.
Dividends paid in the form of shares are called Stock Dividends.
Normally fast growing companies or just started companies do not pay dividends at all as they reinvest profits for further growth.