Various institutes offer certificates of ESL or EFL teaching. Some are as short as one month long. I have met teachers with these certificates and was left wondering what they possibly teach in these programs.
I kind of feel that if a person speaks English well and is able to inspire and encourage learners, the ESL/EFL certificate is irrelevant.
Just wondering what others think.
The ability to speak, read, and write English fluency is paramount for ESL. If you can do that, you're at least 99% qualified to teach, depending on your natural aptitude and inclination.
The formal courses provide a framework for true beginners and a few pointers for people with teaching experience. More importantly, they provide a piece of paper, and as we all know, most people are more interested in pieces of paper than they are in true skills.
Some schools/clients will insist on certification (and perhaps even on specific certificates), others don't care. Those that do want them either before of the aforementioned credentialism (they don't know what the certificates represent, but they feel compelled to demand _something_), or because (in the case of schools) they'd like some evidence of at least basic teaching ability (which one must have, naturally or otherwise, in order to get through these courses).
The short courses are very intensive. Sometimes the same course is offered as one month or six months or whatever; the difference is in scheduling, that's all (that is, the same information is covered, roughly, no matter what the duration in calendar days). The shortest versions have the advantage of being less expensive (because you take up a chair in the school for fewer days), but they are also extremely exhausting, and some people may wash out from the heavy workload alone.