The lighting of a unity candle is a relatively recent addition to the traditional wedding ceremony.
The unity candle ceremony uses two taper candles with a large pillar candle (called the "unity candle") in the center. At the beginning of the wedding ceremony, a representative from each family (usually the mothers of the bride and groom) light the two taper candles. Later in the ceremony (usually after the formal vows), the bride and groom use the two taper candles to light the large pillar (unity) candle together.
Often a unity candle is decorated with the wedding invitation, an inscription, a picture of the couple, or other ornamentation. The candles are almost always white. The lighting ceremony may be accompanied by special music, an explanation of the symbolism, or just some period of mutual gazing by the happy couple. In some circles, it is customary for the couple to save the unity candle and relight it on anniversaries.
It is sometimes performed to symbolize the joining together of the two families, and their love for the bride and the groom, into one united family that loves the new husband and wife. More often it is to symbolize the union of two individuals, becoming one in commitment. The popular explanation is that the taper candles are lit by representatives from each family to symbolize the love and allegiance that each family has for either the bride or the groom. As the bride and groom use these two flames to light the unity candle, they bring the love of both families together in a united love of the new couple. Generally, the two tapers are left burning and replaced in their holders (because each family's love for their own will continue). However, in some ceremonies they may blow out their individual candles.
When the ceremony is alternatively performed to symbolize simply the joining together of the bride and groom, the tapers may be blown out, to indicate that the two lives have been permanently merged, or they may leave them lit beside the central candle, symbolizing that the now-married partners have not lost their individuality.
Unity Candle Ceremony
(Groom) and (Bride), the two lighted candles symbolize your separate lives, your separate families and your separate sets of friends. I ask that you each take one candle and that together you light the center candle. The individual candles represent your individual lives before today. Lighting the center candle represents that your two lives are now joined to one light, and represents the joining of your two families and sets of friends to one. (Groom) and (Bride) will now extinguish their own candles, thus letting the center candle symbolize the union of their lives. As one light cannot be divided, neither will their lives be divided.