AFS is an international, voluntary, non-governmental, non-profit organization that provides intercultural learning opportunities to help people develop the knowledge, skills and understanding needed to create a more just and peaceful world.
It is important to stress that there is a major difference between language learning programs and intercultural programs. While in the latter you also learn to master (and dream!) a language, the former will put you in one classroom full of other foreigners, even if you stay in a family.
Intercultural programs will allow you to dive into a family (as a member, not as a paying customer), into a local school and into local communities. You will learn to move in the new culture, and not only to move with other foreign language students.