In a nutshell, Ash Wednesday is the first day of Lent, which happens 46 days before Easter (40 days, excluding Sundays) Ash Wednesday can happen as early as February 4th, and as late as March 10th.

Ashes are placed on the forehead of Christians as a reminder and celebration of human mortality, and as a sign of mourning and repentance to God. The ashes used are typically gathered from the burning of the palms from the previous year's Palm Sunday.

Lent celebrates the 40 day period in which Jesus spent fasting in the desert and resisting Satan's temptation. Most Christians will give up one favorite activity, luxury, or vice in honor and remembrance of this event. Lent is also a time of fasting, reflection, prayer, penance, repentance, alms-giving, and self-denial.

The major Christian sects that celebrate Lent are: Catholics, Anglicans, Lutherans, Methodists, and some Baptist denominations.