Teaching about Fasting.
16"When you fast,* do not look gloomy like the hypocrites. They neglect their appearance, so that they may appear to others to be fasting. Amen, I say to you, they have received their reward.
17But when you fast, anoint your head and wash your face,18so that you may not appear to be fasting, except to your Father who is hidden. And your Father who sees what is hidden will repay you.
Catholics fast for Lent and so do Greek Orthodox. Some Protestants do to but that seems to be an individual choice.
Catholics must fast on Ash Wednesday and Good Friday under pain of sin. Catholics are encouraged, but not obliged to fast throughout the entire duration of Lent, save on Sundays. On Fridays during Lent, Catholics must abstain from meat.
Lent is observed starting Ash Wednesday, and lasting until Easter. The day before lent starts is Mardi Gras (Fat Tuesday) which, since many Catholics fast during lent, was when Catholics would eat tons of food preparing for their fasting.
You don't fast during Easter. Catholics, Orthodox and some other Christians fast from meat during Lent: Catholics on Ash Wednesday and every Friday in Lent. Orthodox fast from meat every day during Lent. The Lenten fast ends on Holy Saturday night with the celebration of the Easter Vigil. The purpose of the fast is to discipline the body and focus on the spiritual life.
That depends on what form of Christianity you are talking about. Some Catholics fast during Lent, but most of the other forms never fast.
The period of Lent.
Roman Catholics may not eat meat during a day of fast (Ash Wednesday, the Fridays of Lent, etc.) Otherwise, Catholics have no dietary restrictions.
Lent is a time of public penance for Catholics. Catholics between the ages of 18 and 59 should fast on Ash Wednesday and Good Friday. Catholics 14-years and older should not eat meat on Ash Wednesday, Good Friday, and every Friday during Lent.
Catholics age 14 and up must refrain from eating meat on Ash Wednesday and all Fridays during Lent.
"to fast" means to refrain from eating (possibly only some some foods), so, for example, "Catholics sometimes fast during Lent".
They fast for lent. Lent is 40 days between ash Wednesday and Easter.
Catholics are required to fast on Ash Wednesday and Good Friday.