Different as they are, advertisements are alike in one important way. They have the same purpose :to get people to buy something.
In the days of the cave men there was no advertising. There was no need for it. But as soon as people began to make things to sell, advertising was found to be useful. The merchants of ancient Egypt hired "criers" to walk through the streets shouting or singing about the things they wanted to sell. Newsboys still "cry" their papers now. The barkers at a circus are criers, too.
In the Middle Ages merchants hung picture signboards over their shop doors showing what they had to sell. A large picture of a shoe above a shop door meant that it was a shoemaker's shop. It suggested buying shoes or having old ones mended.
