Ash Wednesday marks the beginning of the Season of Lent. It is a season of penance, reflection, and fasting which prepares us for Christ's Resurrection on Easter Sunday, through which we attain redemption.
Ash Wednesday is one of the most popular and important holy days in the liturgical calendar. Ash Wednesday opens Lent, a season of fasting and prayer.
Ash Wednesday takes place 46 days before Easter Sunday, and is chiefly observed by Catholics, although many other Christians observe it too.
Ash Wednesday comes from the ancient Jewish tradition of penance and fasting. The practice includes the wearing of ashes on the head. The ashes symbolize the dust from which God made us. As the priest applies the ashes to a person's forehead, he speaks the words: "Remember that you are dust, and to dust you shall return."
Alternatively, the priest may speak the words, "Repent and believe in the Gospel."
Ashes also symbolize grief, in this case, grief that we have sinned and caused division from God.
Writings from the Second-century Church refer to the wearing of ashes as a sign of penance.
Priests administer ashes during Mass and all are invited to accept the ashes as a visible symbol of penance. The ashes are made from blessed palm branches, taken from the previous year's palm Sunday Mass.
It is important to remember that Ash Wednesday is a day of penitential prayer and fasting. Small children, the elderly and sick are exempt from this observance.
It is not required that a person wear the ashes for the rest of the day, and they may be washed off after Mass. However, many people keep the ashes as a reminder until the evening.
Why we receive the ashes
Ashes are a symbol of penance made sacramental by the blessing of the Church, and they help us develop a spirit of humility and sacrifice.
The distribution of ashes comes from a ceremony of ages past. Christians who had committed grave faults performed public penance. 
The Ashes
The ashes are made from the blessed palms used in the Palm Sunday celebration of the previous year. The ashes are christened with Holy Water and are scented by exposure to incense. While the ashes symbolize penance and contrition, they are also a reminder that God is gracious and merciful to those who call on Him with repentant hearts. His Divine mercy is of utmost importance during the season of Lent, and the Church calls on us to seek that mercy during the entire Lenten season with reflection, prayer and penance.
Edited version © Catholic Online