Ordinary shares give their holders the right to receive dividends, only after dividends on preference shares where paid. In case of bankruptcy, bondholders, creditors and preference shareholders will have preference over ordinary shareholders.
Ondinary shares five their owners the right to vote on some matters like electing the board of directors. The share of votes is proportional to the share of ordinary shares. The large number of small shareholder makes them difficult to organize. This is usually why only the biggest investors have some influence on important decisions.