ESL Definition

ESL means "English as a second language". People usually use the word ESL to talk about teaching English to people who do not speak English. Usually, ESL teaching happens in an English-speaking country. Often, ESL students are people who came to live in an English-speaking country, and do not speak English very well. If we talk about teaching or learning English in a country where English is not spoken, we usually use the word "EFL", but "ESL" is sometimes used, too.
Here are some example phrases with the word ESL:

an ESL website
Laura is an excellent ESL student.
Most ESL teachers are native speakers.
Paul goes to an advanced ESL class.
The book is full of boring ESL quizzes and activities.
He was reading an ESL magazine. 

 

 http://www.antimoon.com/terms/esl.htm

 

ESL refers to the learning of English within an English-speaking region, generally by refugees, immigrants and students. (The term has been criticised on the grounds that English may not be someone's second language but their third, fourth, or more.) TESL is the teaching of English as a Second Language.
EFL indicates the learning of English for eventual use in a non-English-speaking region. It can occur either in the student's home country (think of millions of schoolchildren around the world, sweating to achieve the level necessary to read this page as fluently as you are doing now), or, for the more privileged minority, in an anglophone country which they visit as a sort of educational tourist, e.g. after graduating from university back home. TEFL is the teaching of English as a Foreign Language.
If you find all these acronyms confusing, it may help to simplify. ESL tends to concentrate on English for daily needs and for living in an English-speaking community. EFL tends to concentrate on English for academic success (whether in the local school exam system, or for post-graduate study abroad), on exams, and sometimes on using English at work, i.e. within an office where English is sometimes needed.
Part of the confusion is created by the funding structure. Again, as a gross generalisation, in English-speaking countries such as Canada and Britain, the government pays for ESL to integrate newcomers into the wider society, and the individual student or his sponsor (parents, boss) pays for EFL.
It is worth noting that ESL/EAL/EFL programs also differ depending on the variant of English being spoken; "English" is a term that can refer to various dialects, including British English, North American English, and other dialects. For example, students studying ESL/EFL in Hong Kong are more likely to learn British English, especially British idioms, which may make travel to the United States marginally more complex for them, as North American English uses very different idioms and slang. For this reason, many teachers of English as a foreign language now emphasize teaching English as an international language (EIL), also known as English as a ­lingua franca (ELF).

http://www.wordiq.com/definition/EFL