A TEFL (Teaching English as a Foreign Language) certification provides skills needed to teach English in countries where English is not the native language such as Mexico, Japan, and China. A TESOL (Teaching English to Speakers of Other Languages) certification provides skills needed to teach English in countries where English is the native language, such as the USA, UK, and Australia. They both cover a lot of the same topics and content and can be used to teach English anywhere in the world.