Lent begins with Ash-Wednesday when ashes are blessed and distributed. Ash Wednesday gets its name from the practice of placing ashes on the foreheads of the faithful as a sign of repentance.

The ashes used are gathered after the Palm Crosses from the previous year's Palm Sunday are burned.

The number forty has the biblical  meaning: God is creating a new people.

Customs during the time of Lent

There are traditionally forty days in Lent which are marked by fasting, both from foods and festivities, prayer and almsgiving.

the Gloria in Excelsis Deo and likewise, the Alleluia are not sung during the Lenten season, disappearing on Ash Wednesday and not returning until the moment of the Resurrection during the Easter Vigil.

Fasting during Lent was more severe in ancient times than today. In some places, believers abstained from food for an entire day; others took only one meal each day, while others abstained from all food until 3 o'clock. In most places, however, the practice was to abstain from eating until the evening, when a small meal without meat or alcohol was eaten.

In current Western societies the practice is considerably relaxed,
During Lent, Catholics are required to fast and abstain on certain days, in imitation of Jesus’ fast in the desert.  Church law defines “fasting” as eating one regular-sized meal and two small meals. “Abstaining” is refraining from eating animal flesh.  Ash Wednesday and Good Friday are days of both fasting and abstinence, and all Fridays of Lent are days of abstinence from meat.