Human migration can be caused by pull factors or push factors. Pull factors are things that attract people to move somewhere, like a new job, while push factors compel people to leave a place due to problems like war or pollution. Many words discussed relate to migration, such as immigrant, which refers to moving to a new country, and expatriate, which means living outside one's home country. The documents provide personal examples of migration, such as moving with families for a parent's job or leaving a country during a war.