The distribution of ashes reminds us of our own mortality and calls us to repentance. In the early Church, Ash Wednesday was the day on which those who had sinned, and who wished to be readmitted to the Church, would begin their public penance. The ashes that we receive are a reminder of our own sinfulness, and many Catholics leave them on their foreheads all day as a sign of humility.
The Church emphasizes the penitential nature of Ash Wednesday by calling us to fast and abstain from meat. Catholics who are over the age of 18 and under the age of 60 are required to fast, which means that they can eat only one complete meal and two smaller ones during the day, with no food in between. Catholics who are over the age of 14 are required to refrain from eating any meat, or any food made with meat, on Ash Wednesday.