(NEXSTAR) – Ash Wednesday is upon us, which means some may have ashes upon them. Not sure what that means? Let’s explain.

Ash Wednesday is the first day of Lent, the 40-day period leading up to Easter, largely observed by Christians.

On this day, Christians attend mass – typically one of the most well-attended masses, according to Kim Mandelkow, director of the Office for Worship with the Archdiocese of Milwaukee, and Father Martin Schlag, a professor and chair of Catholic social thought at the University of St. Thomas in Minnesota. Ashes from the palms burned on the previous day, Shrove Tuesday, are then used to mark mass attendees.

Usually, the ashes are used to mark a cross on each person’s forehead. Schlag says the ashes are intended to remind Christians at the start of Lent that, “We are mortal.”

The 40-day period of Lent serves as a time for Christians to “engage in acts of prayer, fasting and almsgiving,” Mandelkow explains, in preparation for the celebration of Easter. Why 40 days? It commemorates the same amount of time Jesus spent fasting in the desert before starting his public ministry, according to Schlag.

The word “lent” is an old Germanic word, “lenz,” Schlag explains, which means spring. Because Lent falls during the transition from winter to spring, it also signifies new life, a common theme associated with Easter.

According to Mandelkow, Christians were known to fast for one or two days before Easter. A 40-day fast wasn’t recorded until about the third century in Egypt.

Traditionally, this isn’t a severe fast where Christians can’t eat anything. More commonly, they give up meat, dairy products, eggs and sugar. Some may even give up other indulgences, like alcohol or social media.

Lent will come to an end on Easter, which lands on Sunday, April 17 this year.