Lent is a forty day period during which Christians remember their sinfulness, repent, and recognize afresh the forgiveness that comes from God in Jesus Christ alone. We recognize that God's forgiveness for all of us has come at an infinite price—the death of Christ on our behalf.
As a time of humility, the forty days of Lent correspond to the periods of forty in the Scriptures, such as the forty years in which the Jews wandered in the wilderness, or the forty days that the Ninevites took to repent, or the forty days during which Jesus experienced temptations in the desert.
The final week of Lent culminates in Holy Week, which begins the day after Palm Sunday, memorializing Jesus' triumphal entry into Jerusalem. These forty days are the most important time in the Christian calendar, culminating in commemoration of the atoning work of Jesus Christ on the cross (Good Friday) and His resurrection from the dead on the following Sunday.
This period in particular reminds us that our sin separates us from God, who "demonstrates His own love toward us, in that while we were still sinners, Christ died for us" (Rom. 5:8).