To produce scented candles, fragrance oils are blended with candle wax that has been melted to 125°- 160°.   once hardened, the fragrance oil becomes integrated as part of the wax.
When the candle is lit, the heat given off from the flame will melt the blended wax and begin to create a liquid pool around the wick. This process will release the fragrance oil and the heat will assist to carry the scent throughout the room. The longer it burns, the larger the pool and the more exposed fragrance oil available.