Not sure if this is what you're looking for, but I'll give it a shot.
Morphology, with respect to grammar, is the study of changes in words and language. Morphology is often called the structure of words-as units in the structure of language.
Conversion is a morphological device which involves no morphological change. In other words, conversion (in grammar) changes the function or syntax of a word without changing the word itself. Here's one example, with the stressed syllable in itallics. (from Verb to Noun).
convert and convert. The pronunciation changes, but the grapheme (word) does not.
If by "language and parole," you mean "la langue and parole," from Saussure, then I can give you the basic idea.
La langue is the abstract system of signs and language of a given speech community. Parole is the putting into practice of that language. Langue is language and parole is speaking.
At any one time, when a speaker uses conversion, he/she is using parole but he/she is referring to the most recent rules and structures of his/her language (langue). Since the speaker (parole) and the social/psychological language (langue) he refers to are an interacting duo, changes to languages often result from interaction between the two, or from interaction between two different social groups.
The visual and chess metaphors: This most recent look at the rules and setup of a language system is called the synchronic (the snapshot or setup of the players on the chess board). The look at the whole history of the rules would be called the diachronic (the history of movement, not just the snapshot, or the history of the game of chess.)