English as a Foreign Language: the teaching of English to students whose first language is not English

English for specific/special purposes: the teaching of English for use in a particular area of activity, for example, business or science

English as a lingua franca: the type of English used by speakers of other languages as a way of communicating among themselves

English as a Second Language: the teaching of English to speakers of other languages who live in a country where English is an official or important language