Dear Rosa:

Burning candles have several symbolic meanings such as that of "prayer and sacrifice" and also the "light of Christ".

In the context of Votive Candles the symbolic meaning includes that of prayer in that the heat and smoke of the fire symbolizes that rising of our prayers to God.

This is a devotional way to offer our prayer intentions to God not just in the singular recitation of the prayer but as a continuing prayer for the life of the candle.

Candles were used in the early Church in liturgy. As for the use of candles of votive prayers the beginnings are also early.

A curious medieval practice was that of offering at any favoured shrine a candle or a number of candes equalling in measurement the height of the persons for whom some favour was asked. This was called "measuring to" such or such a saint. The practice can be traced back to the time of St. Radegund (d.587) and later right through the Middle Ages. It was especially common in England and the North of France in the twelfth and thirteenth centuries.
(source: 1917 Catholic Encyclopedia)

God bless,
Bro. Ignatius Mary