why does advertising exist

Advertising has been used  through out our history to show people what you are selling. People advertise to show what they are selling a company like specsavers get lots of money because they advertise their products alot on tv . If you do not advertise your products you will not make much money as a company which do advertise. If no one advertises you will not know what people are selling and companies would make less money than they should. However with advertising companies would make more money