A shares are ordinary shares with limited voting rights or no right to vote at all. A company may be set up with two classes of share: A shares, which are available to the general investor, and B shares which are only bought by certain individuals, such as the founder and his or her family. Such division of shares is becoming less usual nowadays.
Share of audience is the percentage of homes using TV tuned to a particular program or station. Share of market is the percentage of total category volume, accounted for by a brand. Share of voice is the percentage of advertising impression generated by all brands in a category accounted for by a particular brand but often also refers to share of media spending.