A popular known custom is the sharing of the "oplatek" (also known as "Angel Bread") in the last days before Christmas, especially on Christmas Eve.

Beginning the Church's liturgical year, Advent (from, "ad-venire" in Latin or "to come to") is the season encompassing the four Sundays (and weekdays) leading up to the celebration of Christmas.

Advent is a time of preparation that directs our hearts and minds to Christ’s second coming at the end of time and also to the anniversary of the Lord’s birth on Christmas. The final days of Advent focus particularly on our preparation for the celebrations of the Nativity of our Lord (Christmas).

The four weeks of Advent are popularly considered to symbolize the four thousand years of darkness before the coming of Christ. We set up Nativity scenes, light Advent candles, and
decorate wreaths in our homes to signify Christ’s presence coming in the darkness of sin and suffering. Four candles adorn an Advent wreath, one for each week. A fifth candle is sometimes placed in the center for the beginning of the Christmas season. Advent devotions including the Advent Wreath remind us of the meaning of the season.

Advent colors are worn by the priests and deacons and decorate the church. They are represented in the candles that surround the Advent wreath:

Violet: royalty, repentance, and fasting (First, Second, and Fourth Week of Advent)

Rose: abundant joy (Third Week of Advent, known as Gaudete Sunday, joy in Latin)

White: light and purity (Christ Candle, center candle completes the season and begins Christmas)

An Advent calendar can help you fully enter in to the season with daily activity and prayer suggestions to prepare you spiritually for the birth of Jesus Christ. Click to Download the Advent Calendar shared via USCCB English  / Spanish.

To learn more about Advent check out this article shared by Loyola Press, "About Advent." Additional Advent resources are listed below. 

Advent Resources

• Calendar
• Blessing of an Advent Wreath
• Blessing of a Christmas Tree
• Commentary on the Proper Prayers of Advent from the Roman Missal
• Blessing of a Christmas Manger or Nativity Scene
• Festival of Lessons and Carols
• Lectio Divina for Advent
• The "O Antiphons" of Advent

Related Links: 

Advent Activities for All

Have you blessed your Christmas ornaments? Learn more. 

Each begins with a traditional title for Christ. They are: "O Wisdom," "O sacred Lord," "O Flower of Jesse's Stem," "O Key of David," "O Radiant Dawn," "O King of all the nations," and finally, "O Emmanuel" which means "God with us." A magnificent theology that uses ancient biblical imagery drawn from the messianic hopes of the Old Testament to proclaim the coming Christ as the fulfillment not only of Old Testament hopes, but present ones as well; they introduce the Magnificat, or canticle of Mary, at evening prayer from the Liturgy of the Hours, from December 17th through December 23rd. Their repeated use of the imperative "Come!" embodies the longing of all for the Divine Messiah. Click for more via United States Conference of Catholic Bishops.