Stephen Krashen presented his first of five hypotheses about second language acquisition as The Acquisition-Learning hypothesis. And distinct the differences between acquiring and or learning a language is a little bit confusing in my opinion, so I will try to elude it here in the easiest way I can.
According to Krashen, there are these two ways to develop second language ability:
By acquisition is a natural, subconscious process. It seems like when you were a child and acquired your mother tongue: you didn’t need to think about it. You were just receiving and automatically producing. The same principle is applicated in second language acquisition. The acquirers are not aware that they are receiving a lot of information. But the difference between acquiring language when you were a child and as an adult is that the language area closes at a certain age. It means that it was much easier before.
The acquisition process happens mostly because of the environment around the acquirer. If everything around you provides you to use the target language to communicate, pushes you to practice all the time, you are acquiring even if you didn’t think you were. For example, imagine that you had to move out to another country, but you don’t know the language. When you are there, you will be surrounded by people speaking that language and will have to use it. You decide not to go to a language school, because your only goal is to communicate. You won’t be worried about the grammar structure, you will just receive a lot of inputs and your mind will process them and create your own rules, your internal dictionary, so you will follow your instincts to use that language.
Language acquisition is a subconscious process in two senses: people are often not aware that they are acquiring a language while they are doing so. What they are aware of is using the language for some communicative purpose. Also, they are often not aware of what they have acquired; they usually cannot describe or talk about the rules they have acquired but they have a “feel” for the language. (Brown et al., 1973)
On the other hand, by learning is like when we are developing our grammar knowledge in the school. In this case, the process is unnatural. It is conscious and needs a lot of practice. We can say that it is more formal. This way, you are aware that you are learning, because you are taught the rules and become able to talk about them. In this one, the closure of the language area brings the same problem as in the acquiring process, it becomes more difficult after this happens, but not impossible though.
In this hypothesis, the learning process uses error correction as a facilitator of the mental representation of the rule. Let’s go to the example: imagine the same situation presented before, but this time you decide to go to a language school. There you will be taught the rules. You’ll be corrected and won’t need to follow your instincts to use the language, because you will have the knowledge of the language structure.
Language learning is different. It is knowing about language or formal knowledge of a language. Language learning is thought to profit from an explicit presentation of risks and from error correction. Error correction, supposedly, helps the learner come to the correct conscious mental representation of a rule. There is good evidence, however, that error correction does not help subconscious acquisition (Brown et al., 1973).
In everyday terms, acquisition is picking up a language. Ordinary equivalent for learning includes grammar and rules.
An informal way to describe this two process is that the acquisition is like picking up the language and learning we can say that is like the structure of the language.
By T. H. M. Farias
REFERENCE
BILASH, Olenka. Krashen’s 6 Hypothesis. 2009. Available on: <https://sites.educ.ualberta.ca/staff/olenka.bilash/Best%20of%20Bilash/krashen.html> Access on Nov 24th, 2018.
KRASHEN, Stephen D. (1982). Principles and Practice in Second Language Acquisition (PDF). Oxford: Pergamon. Available in: <http://www.sdkrashen.com/content/books/principles_and_practice.pdf>. Access on Nov 24th, 2018.
LEYBA, Charles (Editor). Schooling and Language Minority Students: A Theoretical Framework Evaluation, Dissemination, and Assessment. Center California State University, Los Angeles, 1994. Available on: <https://linguisticsined.files.wordpress.com/2016/05/krashen-bilingual-education.pdf> Access on Dec 03rd, 2018.
Krashen's Second Language Acquisition Theory 