A stuent exchange program is a program in which a student, typically in secondary or higher education, chooses to live in a foreign country to learn, among other things, language and culture. These programs are called 'exchanges' because originally the goal was an exchange of students between different countries. No trade off is actually required, so a student is allowed to go to another country without finding a counterpart in that country to exchange with. Students live with a host family, who are usually unpaid volunteers and can be a traditional family, a single parent, or a couple with no children at home. Host families are vetted by the organization co-ordinating the program. In the United States, the Department of State requires that each person 18 or older in a host family receive a criminal background check.