None already explain the technical and etymological difference.
The main difference is that in European French, or at least in France, chandelle is mostly used nowadays in set expressions, some of them already mentioned earlier in comments:
- brûler la chandelle par les deux bouts: to burn the candle at both ends, to do things in excess, to waste
- voir trente-six chandelles: to see stars, to be knocked out
- dîner aux chandelles: romantic dinner
- tenir la chandelle: "to hold the candle", to be a third wheel
- devoir une fière chandelle: to owe a great deal to someone.
- le jeu n'en veut pas la chandelle: something isn't worth the effort
- économies de bouts de chandelle: penny-pinching savings
As you can see, there are plenty of such idioms so the word itself is well alive, despite being almost unused alone. In the few cases where it is, the meaning is figurative:
- monter en chandelle/descendre en chandelle: to zoom (plane)
- faire une chandelle: to lob (e.g. tennis) or to throw a ball vertically (soccer and other sports), up and under, infield fly, pop fly, pop up, moon ball
- faire la chandelle: shoulderstand
- mettre une voiture sur des chandelles: to use jack-stands
As you can see, there are plenty of such idioms so the word itself is well alive, despite being almost unused alone.
The derived words chandelier/candelabre are also mostly used for antiques and substituted by bougeoir for current candle holders.
There is also a third word, cierge, specialized for candles to be lit in a church.
Canadian French kept chandelle as its main word for candle and mostly reserves bougies for spark plugs. That means in Québec, you would more likely hear souffler ses chandelles while in France, that would be souffler ses bougies. Both expressions are of course understood everywhere.
