Teaching English as a Second Language: ESL is the original acronym that was used to describe an English language learner. The original context of an ESL student was when: Learners study and/or live in the target language community (e.g. Britain, Canada, the USA, etc.). Learners have to function and survive using English outside of the classroom and in everyday society. However, ESL has grown to encompass any learner who is learning English as an additional language in any context.
Teaching English to Speakers of Other Languages: This is a new acronym created to encompass the notion of teaching English as a world language for international communication and for a more multilingual global reality. A TESOL training program is essentially the same as a TESL or TEFL program. There are many MA TESOL programs offered at universities. These are very similar to the more traditional Applied Linguistics Degree.
Teaching English as a Foreign Language: Technically and originally, this is a term used to describe the situation when English is studied in a learner’s native country and is not the primary language of the dominant society. Often the only chances for English practice are in the language classroom and not outside. However, these days the term often describes teacher training programs that are shorter in length or programs that are designed for teachers who are not native speakers of English (English is not their first language). It can also describe a training program that is equivalent to a TESL program.