There are some differences between American English and British English. How did these differences come about?
Many years ago, lots of British people were forced to leave their country and go to some other places. These places were later called America, Canada and Australia. The English language was brought to these places by them. In the beginning, those living in America (later called Americans) spoke the same as they did in England, but the English people at home changed their language. Sometimes Americans spoke in a different way, while the people in England spoke the same as they did before. So the language changed little by little in different parts of the world.
The English language has also taken in many new words from other languages. For example, Americans borrowed "cent" from old French and "cookbook" from German. They also borrowed "tofu" and "kowtow" from Chinese. In short, the English language is changing all the time.