Basically put, a company can sell different types of shares. I forget the names of the various types (and they occasionally make up new ones) but the point is you can sell a share with voting rights for more than a share without; if you want to raise some money but don't want to dilute control of the company, you issue shares without voting rights but get less money for them (or have to issue more shares).
Shares without voting rights in theory still have some value as a) the company should still pay a dividend on them so you get some money back and b) if the company does well, even non-voting shares will go up in value, so you can make a profit on your investment if you sell them on.
I have the words 'preferential' and 'ordinary' in my head but I can't remember exactly what the terms mean in this context. Knowing the Orwellian way things work in the city, it's entirely possible 'preferential shares' are the non-voting ones...
Jon
