Language acquisition is the ability of the brain in its cognitive development & process to conceptualize concepts,structures and semantics in a language , while learning is the active participation and effort to learn a language. Language teachers devise methods as components of language acquisition, while learners use them to learn. Language acquisition is a natural process for any native to acquire his native vernacular language.Language learning is a structured system for anyone to learn a language.

According to Stephen Krashen's acquisition-learning hypothesis, there are two independent ways in which we develop our linguistic skills: acquisition and learning. Acquisition of language is a subconscious process of which the individual is not aware. One is unaware of the process as it is happening and when the new knowledge is acquired, the acquirer generally does not realize that he or she possesses any new knowledge. According to Krashen, both adults and children can subconsciously acquire language, and either written or oral language can be acquired.This process is similar to the process that children undergo when learning their native language. Acquisition requires meaningful interaction in the target language, during which the acquirer is focused on meaning rather than form. Learning a language, on the other hand, is a conscious process, much like what one experiences in school. New knowledge or language forms are represented consciously in the learner's mind, frequently in the form of language "rules" and "grammar" and the process often involves error correction. Language learning involves formal instruction, and according to Krashen, is less effective than acquisition. (source wikipedia) I studied it at university and found it very interesting, hope it helps...