TESOL is an acronym for Teaching English to Speakers of Other Languages.
TEFL is an acronym of Teaching English as a Foreign Language.
Both of these are synonymous and refer to the same thing. There is also no one single body that exists, governing TESOL or TEFL courses.
CELTA, however, is the world's most recognised TESOL or TEFL course and is offered by the University of Cambridge (UK). The numbers speak for themselves.
