The many acronyms used in the field of English teaching and learning may be confusing. English is a language with great reach and influence; it is taught all over the world under many different circumstances. In English-speaking countries, English language teaching has essentially evolved in two broad directions: instruction for people who intend to stay in the country and those who don't. These divisions have grown firmer as the instructors of these two "industries" have used different terminology, followed distinct training qualifications, formed separate professional associations, and so on. Crucially, these two arms have very different funding structures, public in the former and private in the latter, and to some extent this influences the way schools are established and classes are held. Matters are further complicated by the fact that the United States and the United Kingdom, both major engines of the language, describe these categories in different terms: as many eloquent users of the language have observed, "England and America are two countries divided by a common language." (Attributed to Winston Churchill, George Bernard Shaw, and Oscar Wilde.) The following technical definitions may therefore have their currency contested.

EFL, English as a foreign language, indicates the use of English in a non-English-speaking region. Study can occur either in the student's home country, as part of the normal school curriculum or otherwise, or, for the more privileged minority, in an anglophone country that they visit as a sort of educational tourist, particularly immediately before or after graduating from university. TEFL is the teaching of English as a foreign language; note that this sort of instruction can take place in any country, English-speaking or not. Typically, EFL is learned either to pass exams as a necessary part of one's education, or for career progression while working for an organisation or business with an international focus. EFL may be part of the state school curriculum in countries where English has no special status (what linguist Braj Kachru calls the "expanding circle countries"); it may also be supplemented by lessons paid for privately. Teachers of EFL generally assume that students are literate in their mother tongue. The Chinese EFL Journal [3] and Iranian EFL Journal are examples of international journals dedicated to specifics of English language learning within countries where English is used as a foreign language.

The other broad grouping is the use of English within the Anglosphere. In what theorist Braj Kachru calls "the inner circle", i.e. countries such as the United Kingdom and the United States, this use of English is generally by refugees, immigrants and their children. It also includes the use of English in "outer circle" countries, often former British colonies, where English is an official language even if it is not spoken as a mother tongue by the majority of the population.

In the US, Canada and Australia, this use of English is called ESL (English as a second language). This term has been criticized on the grounds that many learners already speak more than one language. A counter-argument says that the word "a" in the phrase "a second language" means there is no presumption that English is the second acquired language (see also Second language). TESL is the teaching of English as a second language.

In the UK, Ireland and New Zealand, the term ESL has been replaced by ESOL (English for speakers of other languages). In these countries TESOL (teaching English to speakers of other languages) is normally used to refer to teaching English only to this group. In the UK, the term EAL (English as an additional language), rather than ESOL, is usually used when talking about primary and secondary schools.