Communicative competence, a term coined in 1966 by Dell Hymes, refers to the ability to use language to communicate effectively. There are several components of communicative competence.
Linguistic competence involves knowing the phonological and grammatical rules of language, as well as understanding vocabulary and syntax.
Sociolinguistic competence is the ability to use language appropriately in certain settings or in regards to certain topics. This can extend beyond words and into body language.
Strategic competence is the understanding of how to repair breakdowns in communication. This can involve clearing up misunderstandings and explaining one's meaning when vocabulary is unknown.