Advent has two different but related meanings:

It means the anticipation of something big. 
And it is the arrival or introduction of something big. 

We live in the in-between age of Jesus’s first advent (our candles and trees and gifts and a baby born in a manger) and his second. We celebrate AND we anticipate.

In a third way, on Communion Sunday, we celebrate the advent of our salvation (not usually stated like that.) The cross and all it entails marks the beginning — the advent — of the means of our salvation.

sermon: Advent-Hope (Hebrews 6:18-20) with Pastor David Donaldson