What is the difference between First Language, Second Language a

What is the difference between First Language, Second Language and Foreign Language?
【正确答案】：First language is one that a person is born and brought up with, and thus it plays a more important role in an individual's cognitive and social development because for the majority of very young children it is perhaps the only, or at least the most important means of communicating with others and of receiving information from the surrounding environments.
Second Language refers to language that is acquired and/or learned in the naturalistic setting after one has already had a relatively good command of his first language. Second language is less important than first language in that it does not play an equally important role in one's cognitive and social development. It is similar to first language in that learners generally have a more or less equally strong need to communicate in it (but it depends on the specific environment in which one lives and the personality of an individual), and that it is learned and/or acquired in the naturalistic setting and to a large extent through communication.
Foreign language is quite different from the above two in that it is generally learned in a conscious way through formal instruction. Learners do not have the target language and cultural context that is necessary for acquisition to happen. Neither do they have the need to communicate in the foreign language.