This document summarizes the key differences between English as a Second Language (ESL) and English as a Foreign Language (EFL). ESL refers to learning English in a primarily English-speaking country, where it is important for survival and daily life. ESL classes have mixed nationalities and no shared native language. EFL refers to learning English in one's home country, where English is not necessary for daily life. EFL classes have a shared native language and culture, and English is learned through a notion-based approach rather than a function-based one.