Usually used, as most French terms - je ne sais pas, ennui, to describe that certain something that is beyond normal language.
Nowdays it is often referred to (incorrectly) as X-factor
However Savior faire suggests a certain style, accomplishment and refinement. A person who has Savoir faire is naturally suave and classy, or has the innate abiilty to do or say the right thing at the right time.
or in a more modern context;
The actor George Clooney can be said to have Savoir faire