Corn potatoes sugar horses smallpox (explain what these have in common)

All the mentioned things are the components of Columbian Exchange trade.

The Columbian Exchange refers to the trade of animals, goods, and ideas between the Old World, New World, and the trading of slaves from Africa to the New World. In the process, Columbus introduced various animals and goods to the New World, like wheat, sugar, coffee, rice, pigs, horses, and cows.

He also introduced goods back to the Old World from the New World, like corn, silver, gold, tomatoes, pineapples, chocolate, vanilla, and beans. Unluckily, with the exchange of goods, there was also an exchange of disease, like measles, smallpox, typhus, diphtheria, bubonic plague, influenza, and Scarlett Fever.