Ash Wednesday receives its name from the ashes created by burning palms blessed the previous year on Palm Sunday. The receiving of dead embers is considered an outward sign (defined as a sacrament in the Catholic Church) of an internal state of repentance for one's sins.
This ash-based religious observance is partly based on the practice, found in the Bible, of wearing sackcloth and ashes as a sign of mourning, repentance or both (1913 Catholic Encyclopedia and 1911 Encyclopedia Britannica articles on the observance).
Those who wore sackcloth in the Old Testament as a sign of mourning (either with or without ashes) include the patriarch Jacob (Genesis 37:34). Others who did so are King David (2Samuel 3:31, 1Chronicles 21:16), King Ahab (1Kings 21:27), King Hezekiah (2Kings 19:1), Mordecai (Esther 4:1 - 4), Daniel (Daniel 9:3) and the King of Nineveh (Jonah 3:6). See also Isaiah 58:5, Jeremiah 6:26 and Lamentations 2:10.
Those who observe the day present themselves, while either standing or kneeling, before a priest or other ordained individual to receive ashes on their forehead shaped in the sign of a cross. As the sign of the cross is made, a version of the phrase "Remember man that thou art dust and unto dust thou shalt return" may be spoken. According to some Bible commentaries, Psalms 5, 32, 38 and 143 (with possibly others) are sometimes read on the day.
Preceding the start of Lent is a day known as Shrove Tuesday (also referred to by the French phrase 'Mardi Gras,' which translated means 'Fat Tuesday'). Since Lent is considered a time of fasting and prayer, the day before it starts has been traditionally considered a day to indulge in revelry and eating rich foods (foods that observers will not eat during the Lenten period).
One pre-Ash Wednesday treat, especially popular in areas with a sizable Polish population (Chicago, Buffalo, Toledo, Cleveland, Southeastern Michigan and Milwaukee in the U.S., as well as the city of Windsor in Canada and other locations), is called Paczki (pronounced pawnch-kee). A Paczki is a traditional Polish donut that is typically bigger (at least in the Detroit, Michigan area) and contains more filling than an average sized American-made donut.