ESL - English as a second language
EFL - English as a foreign language
TESL - Teaching English as a Second Language
TEFL - Teaching English as a Foreign Language
If a language is a foreign language to a speaker, it seems obvious that it would be that speaker's second language (or third or forth), so why the differentiation?
The answer is location.
English is considered a foreign language when it is taught or learned in a non-English speaking country; it is considered a second language when it is taught or learned in an English speaking country.
Thanks to 22 Words for bringing this uproarious video to my attention.
However, if the class mentioned in the video is truly EFL, I would think the enrollment counselor would not be speaking English. It would be more semantically correct if the class was ESL, but it wouldn't be as humorous.