Advent is the period leading up to Christmas, as was posted. There are 4 outer and one inner candle on the Advent Wreath - we lit the first of the three purple ones on Sunday at church. The candles represent, let's see,
Week 1: Hope (purple candle)
Week 2: Peace (purple candle)
Week 3: Joy (pink candle)
Week 4: Love (purple candle)

Then on Christmas the middle big white candle appears and is lit, representing Christ, of course!

Advent calendars usually just include the December days leading up to Christmas, but Advent usually starts in November, depending on what day of the week December 25th falls.