joie de vivre means "joy of life". It describes someone who's energetic, cheery, and generally happy. If someone is like that, you might say: "She's full of joie de vivre."
Literally translated, 'Joie de vivre' means the Joy of Living.
It could be used in a sentence such as, "My Joie de Vivre was all but spent, and life felt pretty dark at times."