(Teaching English as a Foreign Language): This means teaching English in a country where the native language is not English. For example, you could use a TEFL certification to teach English in South Korea. TEFL is the most commonly used acronym for a course that qualifies you to teach abroad. It’s also the one you’ll see listed first in most job postings. It is often used interchangeably with the other terms below, though you’ll see that there are, in fact, some differences.
(Teaching English as a Second Language): This refers to teaching English in a country where English is the native language. For example, a TESL certificate could be used to teach Russian immigrants at a language school in the States. This type of qualification is often offered through universities and colleges.
(Teaching English to Speakers of Other Languages): This certificate encompassing both TEFL and TESOL, since it does not specify if those language learners are in an English-speaking country or not. This would seem like it’s the best, but in fact employers abroad do not generally make a distinction between TEFL, TESL and TESOL! As long as you have certification to teach English, you are covered!
(Certificate in English Language Teaching to Adults). This is also called the Cambridge CELTA, and it is a 4-week, onsite TEFL course (not online). Think of it as a “brand name” TEFL certificate, because it is a standardized course developed by the University of Cambridge. It is very highly regarded worldwide, and it has set the standard for many other classroom-based TEFL courses. It is offered in many locations worldwide, and these locations are all authorized training centers for the CELTA. A lot of people believe this is the best course out there, and I agree that it’s excellent; however, many other TEFL courses are also excellent, and will qualify you for just as many jobs as will the CELTA.
(International Diploma in English Language Teaching to Adults). This is another “brand name” TEFL course, and an example of a CELTA-equivalent TEFL course. It was created by Bridge, and it is similar to the CELTA in that it is a standardized, onsite course that includes teaching practice. It will also qualify you for jobs in countries where onsite certification is required.
Online vs. Onsite TEFL courses
Online TEFL courses are—you guessed it—totally online. They do not include face-to-face interaction or practice teaching. Onsite just means in the classroom. In some parts of the world (Europe and the Middle East, for example) onsite certification is practically required; in other places (Central/South America or Asia), online certificates are accepted, too. If you are not sure where you want to teach, I recommend earning an onsite TEFL certification, since onsite certificates are welcomed by employers everywhere.