Blessed morning to all. Here is a  6 minute rundown of how the Latin Church's liturgical calender is set up, and why it is this way :

1) Each new Liturgical Year begins with the first Sunday of Advent ( usually occurring either on the last Sunday of November or the First Sunday of December)

-the reason this is such is that Advent is a time of anticipation; anticipation of The Second Person of the Holy Trinity mixing very closely and intimately with humanity ( i.e. the Christmas Season). We start the liturgical New Year with Advent because it is a time of looking forward.

2) Various seasons occur during the liturgical year: here they are in order: Advent, Christmas, a few weeks of what is called Ordinary Time (will explain in point three), followed by Lent, The Paschal Tridum, The Season of  Easter begins during a vigil on Holy Saturday night and end 50 days later with Evening Prayer on Pentecost Sunday. We then renter Ordinary Time until the first week of Advent.

3) Meaning of each season:

 A. Advent: Anticipation of Christ's Second Coming and reflection and praise because of his Incarnation    
 2012 years in the Gregorian Calendar. The highlighted color is purple because the season is
 particularly focused on Jesus, and because Roman soldjers gave him a purple cloak to wear during his Passion and Cruxifiction.


 B. Christmas: During this time we especially remember God sending His sameness into our world, for our good, though He certainly was not required to do so. We celebrate the The Nativity of  of Our Lord, The changing human mindsets (events and renewals that happen still each day, thankfully) occurring at The Epiphany, the wonderful sign at the Wedding in Cana, and Our Lord's baptism in the River Jordan. The color for the season is white because white is full of light on the color spectrum, and Jesus, Christians hold, is the Light of the World through His Life, Death, and Resurrection. A large percentage of readings from Sacred Scripture come from John, because He loved Jesus so, so, so much.

 C. Ordinary Time: These are the weeks of the year that fall in between official celebrations and
  memorials centered on the saving actions of God. The color is green, because how wonderfully
 does  green invoke the senses of life (Check out "Morning has Broken," a wonderful early 20th
 Century hymn that gives us a picture and concept of life original, life restored, and what life is
 each morning). The Gospel readings focus on Jesus' earthly ministry. They are 34 weeks of
 Ordinary Time each year with 5 to 7 weeks occurring in January or February of each year.

 D. Lent: Lent is a time of refocused prayer. Many Western Christian denominations focus on giving
 to neighbor during this season, just as Christians hold that Jesus gave His Life for our well-being,  
 Eternal Life. ( And indeed He is the only person that could ever give his life for our full
 Redemption.) The color of this season is purple because our eyes, hearts, and minds are turned
 towards Jesus' journey to the Cross. The life changing, for us, Gospel narrative of The
Transfiguration on Mt. Tabor is a Sunday reading during this season.

E. The Paschal Tridum: This period of each year begins after memorials of The  Last Supper
on Holy Thursday. We walk through the Passion of Our Lord with him; we see the way He
carried his Cross and try to carry our sufferings and trails in the same manner: with our heads
held high.

F. Easter: Begins Holy Saturday night, and its color is white because through the Life, Death, and
 Resurrection of Jesus we are "washed whiter than snow, whiter than woven wool (Ps. 51
 and 147).  The firsts readings during this season usually come from The Acts of the Apostles;
 the Accession of Our Lord is celebrated 40 days after His Resurrection. It is usually transferred
 to the Sunday after the fortieth day of Easter so that as many of the faithful as possible can
 join in the celebration. The fiftieth day of Easter is Pentecost, where we remember Jesus
 sending His Spirit to the Apostles and their successors to remain until He returns.