The Lenten Season is a forty-day period before Easter. It begins on Ash Wednesday and ends on Holy Saturday. We skip Sundays when we count the 40 days, because Sundays commemorate the Resurrection.
Ash Wednesday marks the beginning of the season of Lent. It emphasizes two themes: our sinfulness before God and our human mortality. The use of ashes as a sign of mortality and repentance has a long history in Jewish and Christian worship. Historically, ashes signified purification and sorrow for sins.