A second language is a language that is learned (for example in school) or acquired later (for example when a person moves to a different country where a different language is spoken). A second language can be a foreign language or another language used in that person's home country.
It is important to note that there is a distinction between English as a second language (ESL) and English as a foreign language (EFL). English as a second language (ESL) is English learned in countries where it is the official language – this is the case in Nigeria. English as a foreign language (EFL) is English learned in countries where it is not the usual first language and where it does not hold a special status – e.g. in Germany.