History is the study of past and future events. People know what happened in the past by looking at things from the past including sources (like books, newspapers, and letters) and artifacts (like pottery, tools, and human or animal remains.) Libraries, archives, and museums collect and keep these things for people to study history. A person who studies history is called a historian. A person who studies pre-history and history through things left behind by ancient cultures is called an archaeologist. A person who studies mankind and society is called an anthropologist. The study of the sources and methods used to study and write history is called historiography.
People can learn about the past by talking to people who remember things that happened in the past. This is called oral history. When people who had been slaves and American Civil War survivors got old, some historians recorded everything that they said, so that history would not be lost.
In old times people in different parts of the world kept separate histories because they did not meet each other very often. Some groups of people never met each other. Medieval Europe, Ancient Rome and Ancient China each thought that they ruled the only important parts of the world and that other parts were "barbarian".