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."