sina rashidyani's Key Ideas from Principles and Practice in Second Language Acquisition
by Stephen D. Krashen

The acquisition-learning distinction is perhaps one of the more fundamental hypotheses when it comes to second language studies. It maintains that adults have two distinct and independent ways of developing competence in a second language.

The first way is language acquisition. Language

acquisition is a subconscious process; language acquirers are not usually aware of the fact that they are acquiring language, but are only aware of the fact that they are using the language for communication.

The result of language acquisition, acquired competence, is also subconscious.

We are generally not consciously aware of the rules of the languages we have acquired. Instead, we have a "feel" for correctness.

Grammatical sentences "sound" right, or "feel" right, and errors feel wrong, even if we do not consciously know what rule was violated.