What's the difference between EFL and ESL?

A friend of my asked me the question, "What's the difference between EFL and ESL?" Honestly I couldn't have told you the answer before doing a master's in TESOL (yet another acronym = teaching English to speakers of other languages!) but now I know it is simple: ESL, or English as a Second Language, is the English language as taught to non-native English speakers in an English speaking country, such as the USA, England, Australia, etc. EFL, or English as a Foreign Language, is the English language as taught to non-native English speakers in a country where the official language is something other than English, such as in Japan, Mexico, Thailand, China, etc. The purposes of learning ESL and EFL are different, since a person learning English in the USA probably wants to integrate and learn English to get a good job. However, students learning EFL probably have to know English for a college entrance exam, but have little chance to actually use English with "real" English speakers. Learning English may help EFL students get a better job, but this is not usually a top priority. Many EFL students choose to study English as a hobby. So teaching ESL is actually different from teaching EFL, but they are both basically English but with slightly different student goals.