What is Advent?

I'm stealing this snippet from a post by Elizabeth Kaeton on the movie Golden Compass:

Civil rights leader Howard Thurman set the stage for us to know this Christ when he wrote of Advent and Christmas as seasons of hope. "When the song of the angels is stilled," he said. "When the star of the sky is gone. When the kings and princes are home. When the shepherds are back with their flocks. The work begins … To find the lost. To heal the broken. To feed the hungry. To rebuild the nations. To bring peace among people. To make music in the heart."

Go read her full post if you like. It was from a sermon delivered on Dec 16, Rose Sunday. I'm not sure exactly why it's called Rose Sunday. However, we (Episcopalians and I'm not sure who else) have a wreath with four candles, and we light one each week of Advent. Three are purple and one is pink (or rose). Something like that.