Ash Wednesday is one of the most important days in the liturgical calendar for Catholics and many other members of the Christian faith. It signifies the beginning of Lent: the season of reflection, prayer and fasting. It is always 46 days before Easter Sunday, since it represents the 40 days that Jesus was tempted in the desert. Sundays are not included in the count.
Ash Wednesday originates from the Jewish tradition of penance and fasting, which includes the wearing of ashes on the forehead. The ashes symbolize the dust from which God made us and are made from blessed palm branches, taken from the previous year's palm Sunday Mass. The priest administers ashes during Mass and all are invited to accept the ashes as a visible symbol of penance. Unlike its discipline regarding the Sacraments, the Catholic Church does not exclude from receiving ashes; those who are not Catholics, those who have been excommunicated are not forbidden to receive them since they are not a Sacrament.
It is not mandatory to wear the ashes for the rest of the day, and it can be washed off after Mass, however, many recipients wear their ashes as a reminder for the rest of the day.