When you win, the board explodes into a Candy-frenzy! This is called “Sugar Crush”, which clears the board of any remaining Boosters, plus triggers any which have been created in the final cascade of candies.
All these extras will add to your final points score at the end of the level, so they can help you if you're chasing that important highest score when playing against friends!
Gif showing the end of a level, with a Sugar Crush as described, and Tiffi appearing at the end announcing the level is completed