Linguistic competence is the system of linguistic knowledge possessed by native speakers of a language. According to Chomsky, competence is the ideal language system that enables speakers to produce and understand an infinite number of sentences in their language, and to distinguish grammatical sentences from ungrammatical sentences. This is unaffected by "grammatically irrelevant conditions" such as speech errors. In Chomsky‘s view, competence can be studied independently of language use.
The term linguistic performance was used to describe "the actual use of language in concrete situations". It is used to describe both the production, sometimes called parole, as well as the comprehension of language.
Part of the motivation for the distinction between performance and competence comes from speech errors: despite having a perfect understanding of the correct forms, a speaker of a language may unintentionally produce incorrect forms. This is because performance occurs in real situations, and so is subject to many non-linguistic influences. For example, distractions or memory limitations can affect lexical retrieval and give rise to errors in both production and perception or distractions. Such non-linguistic factors are completely independent of the actual knowledge of language, and establish that speakers‘ knowledge of language (their competence) is distinct from their actual use of language (their performance).