On an exchange you are enrolled just like a regular student at the foreign institution you attend. Because there's less support, they're best for confident travelers who like to solve problems independently. There are limited offerings, but they're economical. Their applications are typically due the term before you go.
A funny story: a friend was trying to tell her host mother that "She was sorry that to have been a bother to her," but a small mix up instead produced, "I'm sorry that you are deranged."
-- Sam Zerbib, France