Advent is the time of preparation for Christmas, the birth of Jesus Christ.
Advent is just over 4 weeks long, beginning four Sundays before Christmas and ending on Christmas Day, when the Christmas Season begins.
Advent is the beginning of the new liturgical year in the Catholic Church. The liturgical year follows the life of Christ so it would, naturally, start with the birth of Christ.
As a result, Advent is also the end of the period known as ordinary time (ordinal time) in the liturgical year. While ordinary time is spent focusing on the message of Jesus and preparing for His second coming, Advent is a time spent preparing for and celebrating the first coming of Christ 2000 years ago.
It is a time especially focused on Jesus Christ. It can be looked at as a sort of "spring cleaning," a time to prepare your mind, body, and soul to welcome the Lord of all Creation.
"I Desire Mercy not Sacrifice"
In this way Advent is different from Lent, another period of preparation for a monumental period in history. During Lent we practice sacrifice and focus on repentance, whereas during Advent you focus more on practicing mercy and grace.
In doing so we give freely of the blessings we have been given in time, talent, and treasure! Rather than abstaining from a favorite food as a sacrifice, we might share that food with those in need because as we all know, Jesus said:
...Amen, I say to you, whatever you did for one of these least brothers of mine, you did for me ~ Matthew 25:40
The Reason for the Season
It should result in you reflecting the graces you have been given to your loved ones, freely granting the mercy you have been granted to those who wrong you, and being an example of Christ's sacrificial love to those around you.
If there is no impact on those around you, what good is it that you became better? As Jesus said:
You are the light of the world. A city set on a mountain cannot be hidden. Nor do they light a lamp and then put it under a bushel basket; it is set on a lampstand, where it gives light to all in the house. Just so, your light must shine before others, that they may see your good deeds and glorify your heavenly Father. ~ Matthew 5:14-16The end goal of any endeavor in Advent is to put Jesus in your mind, in your heart, and on your lips. It is a time to recenter yourself on the only thing that matters.
This is slightly ironic as you could argue it is the hardest time of year to keep Jesus in focus...what with the gifts, the visits, the carols, and parties.
So prepare your heart, share your joys, enjoy the season, but always be sure you don't lose sight of the reason for the season.
Additional Resources for Your Advent Season
Per usual, Bishop Robert Barron has some incredibly insightful things to say on Advent:
Aleteia published a wealth of of informational resources and media about Advent: