The World Trade Organization (WTO) is like an international club made up of many countries, who all agree to play by some very important rules. The rules set out things like how the countries treat each other when they trade with each other, so that it is fair for everyone. When two countries join the WTO, it is like they are shaking hands and saying to each other: "let's always play fair". For example, if one country wants to export something like cars to another country, the Country who wants to buy the cars needs to agree not to put too many taxes on the cars from the other Country, because this would be unfair. All Countries must agree to treat each other fairly, so everyone can get something from being part of the WTO.