Par excellence is an idiomatic expression used to describe that someone or something has a value of being an example of excellence: Chris is co-worker par excellence (understood in a sense that Chris is preeminent in his profession so he's superior to other co-workers.)

Since "par excellence" always refers to an example of excellence, may also express that someone or something represents tipical or most common properties of its own kind: Google is a web searcher par excellence (understood in a sense that Google is widely spread web searcher, therefore it has became an synonym for Internet itself, though excellent web searcher).

"Par excellence" is rather used in philosophical discussions than in everyday language, due to its philosophical origin. As we saw above it may refers to something superior as also to something which became common, for all that is sometimes difficult to separate both meanings: Kant is a thinker of human's freedom par excellence.