What is the difference between EFL and ESL textbooks?

ESL - English as a Second Language - it is a term used when English is taught in a country where English is not the country's first language. ESL is usually taught by teachers whose native language is English.

EFL - English as a Foreign Language - Is a term used when English is taught in a country where English is not the country's first language. EFL is usually taught by teachers whose native language is not English.

The Millie and New Millennium English series of English language textbooks were developed with the assistance of the British Council.

Ah, I'm from California. I've a friend with a phD in ESL. Many new folk in our land have english as a second potential language, and maybe a third given regional dialect. Some also don't really know spanish (or other "main" languages).

I guess you are just speaking of Britain here.