What are the differences among TEFL, TEYL, TESOL, TESL, CELTA, etc.? In the simplest of terms, they are different levels and methods of teaching English to non-native English speakers. TESL certifications are widely regarded as methods for teachers of non-native English speakers and immigrants to English speaking countries. TESOL and TEFL are geared more toward those who want to teach English in non-English speaking countries. Bingo! That’s me!