English as a Foreign Language or EFL refers to English being learned outside of an English-speaking country. The term applies to the context outside of the classroom in which students are learning English, so , for example, high school students in Korea, may have an instructor who is a native English speaker and nevertheless still have an EFL classroom. The terms ESL and EFL should not be used interchangeably (Brown 134). The delineation between EFL and ESL contexts is an important one because it essentially describes the potential limits and resources available to students, as well as their motivation for learning English. Students in an EFL classroom may have no intention of ever going to an English-speaking country, except maybe as a tourist, and when students leave an EFL classroom, they probably return to an environment in which their L1 is the language of use. Teaching English as a Foreign Language is abbreviated as TEFL.
Brown, H. Douglas. Teaching By Principles. Pearson, 2007.