Candles at Church

Why do Catholics light candles at church?
Dear Inquirer,
Thanks for the question. We light candles during official church services (called liturgy, such as Mass) to indicate the special solemnity of the occasion.
Perhaps you are also referring to those stands which have small banks of candles which people can light (usually within small glass containers, colored or not, and often called "vigil lights"). Often you can find them near a statue or icon of Mary. These are called votive candles and indicate that someone is praying about something particular, either for themselves or on behalf of someone else. The word "votive" can also refer to a promise to pray for someone, as well as a wish or desire for a certain outcome on behalf of someone, such as recovery of health.
These lines have been taken from http://www.cptryon.org/ask/ask/candles.html just for information purpose.