There are two types of candle(s) that are used to count down to Christmas Day in Advent. The first looks like a normal candle, but has the days up to Christmas Day marked down the candle. On the first of December the candle is lit and burnt down to the first line on the candle. The same is done every day and then the rest of the candle is burnt on Christmas day.
Lutheran Churches in Scandinavia used 24 little candles to count down through December from the 1700s.
An Advent Crown is another form of candles that are used to count down Advent. These are often used in Churches rather than in people's homes. The crown is often made up of a wreath of greenery and has four candles round the outside and one in the middle or in a separate place. Sometimes a more traditional candelabra is used to display the five candles.
One candle is lit on the first Sunday of Advent, two are lit on the second Sunday and so on. Each candle has a different meaning in Christianity. Different churches have given them different meanings, but I was taught the following:
The first represents Isaiah and other prophets in the Bible that predicted the coming of Jesus. It also represents “Hope”. The second represents the Bible. It also represents “Peace”. The third represents Mary, the mother of Jesus. It represents “Love”. The fourth represents John the Baptist, Jesus' cousin, who told the people in Israel to get ready for Jesus' teaching. It represents “Joy”.
The middle or separate candle is lit on Christmas Day and represents Jesus, the light of the world. In Germany this fifth candle is known as the 'Heiligabend' and is lit on Christmas Eve.
In many churches, the color purple is used to signify the season of Advent. On the third Sunday, representing Mary, the color sometimes changes to pink or rose.
Taken from https://www.whychristmas.com/customs/advent.shtml.