The goal of language learning is performance with language rather than knowledge about the language. Language learning is not additively sequential but is recursive and paced differently at various stages of acquisition. Language develops in a series of approximations toward native-like norms. Language learning is not the accumulation of perfectly mastered elements of grammar and vocabulary. Thus, learner errors are unavoidable.
Language proficiency involves both comprehension and production.
Comprehension abilities tend to precede and exceed productive abilities. Language is inextricably bound to culture. Language use requires an understanding of the cultural context within which communication takes place. Language learning is complex. Instruction takes into account individual learning styles and rates, and also attends to teaching process strategies for successful learning.