They are for prayer, when the candle is lit ( it must be blessed by a priest) before lighting, as lonf as the candle burns, your prayer is being forwarded to God. Usually and often, a saint is asked to intercede and help with the prayer (pray to for Example : St Francis of Assissi) to insure that you are heard, and that your prayer is continuous.
My mother is a very devout Catholic, I am also, not quite as devout, but I am always absolutely astounded how her prayers are answered.
Example: My older sister's husband was out in the oil field 100 mi west of San Angelo Texas, by himself and had a stroke..only 47 yo at the time. Took 3 hours to realize he was missing, in his parlyzed state he could only touch on his mobile, and then could not talk coherently or hold the phone, laying in the hot west Texas sun next to his pickup. He kept hitting redial, and the last person he had talked to was his mother. Took another 3 hours to find him by helicopter., Careflighted in and unconscious.
We were told he wouldn't make it through the night. My mother had lit 3 candles in prayer to The Holy Trinity upon her and my dad's departure 400 mi away.
He made it through the night, 2 days later had intensive neuro-surgery that lasted 13 hours! Candles were also lit at the local Catholic church in San Angelo.
He makes it through and responds to nothing for a week, and neuro assessments are dismal. More candles.
He finally pulls through but has no neurological on left side...then has an MI!
Goes through a bypass surgery...More Candles.
3 weeks later in ICU he starts spiking a temp...source cannot be found. Finally has exploratory chest surgery done and L lower lung has a huge abcess. More Candles.
This man recovered, has some disabilty on his left side, but can walk and chew gum, even though he does have to make sure the L leg is planted before applying weight, drives, and rides horses regularly. has a raspy voice because of the necrosis and scarring caused by such a long intubation period, but he loves Candles..
Has one in his pickup for him and his dog.