ESL (which means English as a Second Language) and TEFL (which means Teach English as a Foreign Language) essentially mean the same thing, which is teaching English to people who do not speak English as their first language. It means you can: travel the world; interact with a range of new people; learn new skills.
To teach English to those who are not native English speakers you should have a solid grasp of the English language yourself and feel confident in your ability to express and explain what you know to other people.
Having the following attributes will also be of benefit to you: a friendly and confident manner; good time management / planning skills; the ability to work under pressure; flexibility; clear speech / pronunciation.
The main job responsibilities include: preparing and delivering English lessons; assessing students ability and potential; giving students feedback on their work.
Different methods of teaching that can be implemented into your classes include: conversation; comprehension exercises; games; songs; flashcards; role plays; videos; debates; pair work; group projects.
An ESL / TEFL teachers role is focused on conversation, rather than grammar, and it is generally accepted that teachers speak only in English for the duration of their classes; the ability to speak a foreign language not being necessary for teaching English abroad.
The vast majority of ESL / TEFL jobs require you to be a native speaker; this means that either the USA, Canada, Australia, New Zealand, South Africa, Ireland or the UK is your home country, and that English is your first language. You can be any age from 18 to 80; though those under 21 or over 50 may find it more difficult to find a teaching position.
Most ESL / TEFL jobs require you to have a university degree, however, that degree does not need to be an English or teaching related one. You can find ESL / TEFL jobs should you not be a degree holder but you: will only be able to choose from a handful of countries; will likely be offered lesser paid jobs; will have difficulties getting a work permit (which you need to work abroad legally).
ESL / TEFL specific qualifications are not needed in order to teach English abroad, but you will be able to choose from more jobs, and will be paid more, if you have them. A quality ESL / TEFL course program should consist of: a minimum of 100 hours of study; at least 6 hours teaching real students under the supervision of an experienced teacher; accreditation from an overseeing body (a university or examining board).
The most recognized, trusted and preferred ESL / TEFL qualifications are the Cambridge Celta and the Trinity CertTesol. These courses involve: sessions on classroom management and teaching materials; observed teaching practice; assessed written modules.
Online ESL / TEFL courses are seen as an ideal option by some due to their price and flexibility. They offer a good introduction to ESL / TEFL but you should be aware that the majority of these courses are not internationally accredited and as such may not be accepted by future employers as a valid teaching qualification.