These are Saussure's terms. Langue refers to the abstract system of rules and conventions of a signifying system - it is independent of, and pre-exists, individual users. Parole refers to concrete instances of its use. To the Saussurean semiotician, what matters most are the underlying structures and rules of a semiotic system as a whole rather than specific performances or practises which are merely instances of its use. Whilst Saussure did not concern himself with parole, the structure of langue is of course revealed by the study of parole. Applying the notion to semiotic systems in general rather than simply to language, the distinction is one between the semiotic system and its usage in specific texts and practices.