TEFL or teaching English as a foreign language refers to teaching English to students whose first language is not English and is taught in a region where English is not the dominant language and natural English language immersion situations are apt to be few. TEFL usually occurs in the student's own country either within the state school system, or private, either in an after-hours language school or with a one-on-one tutor. The teachers may be native or non-native speakers of English.

The ideal qualification is an undergraduate degree in any subject, plus a certificate in teaching English.

English teaching certifications can be earned through an intensive, 4-week program or longer part time program which is in turn internationally recognized qualification that is accepted by many employers around the world. The CertTESOL and the CELTA are generally the most widely recognized and they are accredited in the UK on the National Qualifications Framework. Both qualifications are accepted by the British Council in their accredited teaching organizations worldwide in 100+ countries. However, there are several international certificate programs which are run by schools in various locations around the world.

As in most fields of work, the rate of pay depends greatly on the candidate's education, training, experience, seniority, and expertise. As with much expatriate (aka "expat") work, the employment conditions vary considerably between countries depending on the level of economic development and the perceived desirability of living in that place. In relatively poor countries, even a low wage may equate to a comfortable middle class lifestyle.

In Japan, the JET Programme employs assistant language teachers to work in Japanese high schools and elementary schools. Other teachers work in private language schools (eikaiwa). The largest of these chains are Aeon, GEOS, and ECC. The industry is not well regulated; Nova, one of the largest chains with over 900 branches, collapsed in October 2007, an incident that left thousands of foreign teachers without money or a place to live. Other teachers work in universities. Agencies are increasingly used to send English speakers into kindergartens, primary schools, and private companies whose employees need to improve their English. Agencies known in Japan as "hakken" or dispatch companies have recently been competing among theselves to get contracts from various Boards of Education for Elementary, Junior and Senior High Schools, so wages have decreased steadily in the last 4 years.

The technique of using literature aimed at children and teenagers for TEFL is rising in popularity. Both types of literature offer simpler material ("simplified readers" are produced by all the major publishers), and are often written in a more conversational style than literature aimed at adults. Children's literature in particular sometimes provides subtle cues to pronunciation, through rhyming and other wordplay. One technique for using these books is called the "multiple-pass technique". The instructor reads the book, pausing often to explain words and concepts. On the second pass, the instructor reads the book completely through without stopping.

Communicative language teaching (CLT) is an approach to the teaching of languages that emphasizes interaction as both the means and the ultimate goal of learning a language. Despite a number of criticisms , it continues to be popular, particularly in Japan, Taiwan, and Europe. Task-based language learning (TBLL) is a particular approach to CLT which has been gaining ground in recent years.