The teachings of the Catholic Church on the liturgical year might be summarized in the following points:

• In the liturgical year the various aspects of the one Paschal mystery unfold. Three moments mark the high points of the Church's liturgical year: Easter (the feast of the resurrection of the Lord Jesus Christ), Pentecost (the descent of the Holy Spirit upon the apostles and the birth of the Church), and Christmas (the birth of the Incarnate Word, Jesus).
• Seasons of fasting prepare us for seasons of feasting. Lent prepares us to celebrate the 50-day season of Easter baptism. Advent prepares us to celebrate the 12 days of Christmas. 
• The Church sets aside other feasts and solemnities to mark the mysteries of the incarnation (e.g. Annunciation, Epiphany) and the celebration of the saints who bear witness to the fruits of the indwelling Spirit. 

Recommended Reading

• Here is a solid overview of the Catholic liturgical year, with information about specific seasons under each link: "The Liturgical Seasons of the Catholic Church."
• Want to nerd out on the liturgical year? Check out James White's "Language of Time" chapter in his Introduction to Christian Worship (Download)
• Here's a slightly more theological take: Adrien Nocent's "Introduction" in his magnus opus The Liturgical Year (Download)
• This website has a wealth of information on the liturgical year. Explore!
• The liturgical year involves times of fasting and feasting. Here's one helpful article on fasting, and another on feasting.
• See the USCCB's Advent page for some helpful resources.
• And also NCR's "A busy Catholic's guide to Advent", Catholic Traditions for Advent and Christmas, and 5 Comforting family traditions that are perfect for Advent.
• This isn't a specifically Catholic resource, but it has a wealth of information about how Christians celebrate the liturgical year:  "Godspace's Introduction to the Liturgical Calendar" 

Weekly Meditation:  Get Ready for Christmas by Observing Advent!

In the Catholic liturgical year, feasts always follow fasts. To take a small example, we fast for at least an hour before we celebrate the Eucharist. On a more major scale, before we celebrate Easter we spend 40 days in Lenten preparation. Fasting hones the mind and body, helping us to dedicate all of our resources to a single task. When we fast, we voluntarily go without some things that we don't necessarily need: luxurious food and drink, entertainment and diversions, extra sleep. Fasting creates space for prayer, both externally and internally.

• Take a minute and reflect on fasting in your own life. Are there times in which you have abstained from inessential things so that you might focus on what is essential? How do you periodically come to recognize and surrender the things which might be distracting you from being in the presence of God?

Before we celebrate Christmas, we set aside the four weeks of Advent (a word which means "arrival" or "coming") as a time to make ourselves ready for the coming of the Lord. When you arrive in church this Sunday, you'll notice that the green colors of Ordinary time that surround the sanctuary and pews have given way to more somber purples -- the same color that we use when we observe Lent. (Indeed, some Catholic and Orthodox believers refer to Advent as a "little Lent.") This is not because Advent is a sad or difficult time (neither, as we will see in the spring, is Lent!), but because Advent is a time of quietness, of preparation, of reflection.

• Take another minute and remember some Advent traditions you have observed. Can you think of any? How do they reflect the meaning of Advent as a time for the church to prepare for the coming of Jesus into our lives? 

As grumpy but well-meaning Catholics often like to point out, the Christmas season doesn't begin until December 25th. You'll hear no Christmas carols at Mass until Christmas, and you'll see no vibrant lights or colorful poinsettia around the altar until Christmas. The commercial world of advertising, consumerism, and entertainment likes to ignore this fact, because Advent doesn't sell. To some extent or another, we all capitulate to the desires of consumer culture to celebrate Christmas early (in my house, for example, we start watching It's Christmas, Charlie Brown the day after Thanksgiving), but we can also find ways to observe Advent faithfully. 

• Take a final minute to choose one Advent practice to which you can commit, a way of setting aside time and space for reflection on the coming of Jesus into the world. You might research some traditional Advent practices like the lighting of the Advent candle or preparing a nativity scene (minus the baby!) with your children. Or you might choose to make Advent a time when you commit to a new or special form of prayer: the Church's evening prayer or the rosary come to mind. Whatever your practice, use it to make the coming weeks a meaningful time of preparation, so that when the Christmas season arrives, you and your loved ones are eager and ready to celebrate.