These EnglishClub TEFL Training pages contain advice and resources for prospective or existing ESL teachers. EnglishClub does not offer TEFL training itself; nor is it associated with any TEFL-training organisation.
Today there are quite a few organizations offering TEFL qualifications. Three of the best known bodies, with externally validated courses, are:
EFL or ESL?
What's the difference between English as a Foreign Language and English as a Second Language?
ELT Abbreviations and Acronyms
A guide to widely used abbreviations and acronyms in ELT terminology