a) What is the fourth precept of the Church?
The fourth precept of the Church is: to abstain from eating meat and to observe the days of fasting established by the Church. Fasting means taking less food than what is usually consumed during meals, in accordance with the norms issued by the lawful Church authority. Abstinence means not taking meat. All Catholics between the ages of 18 and 60 should fast unless they are excused. All Catholics above 14 years of age should abstain unless they are excused.
Fasting and abstinence are observed on Ash Wednesday and Good Friday. All the Fridays of the year are also days of abstinence unless they are solemnities. Except on Ash Wednesday and Good Friday, abstinence may be substituted with exercises of piety, such as reading the Bible, going to Mass, visiting the Blessed Sacrament, and praying the Holy Rosary, or with acts of charity, such as visiting the sick and the imprisoned, giving alms to the poor, and teaching catechism.
b) Why should an Altar Server know and live the fourth precept of the Church?
The Church wants us to fast and abstain so that we may do penance for our sins, practice self-denial, control our senses, and imitate Christ himself, who suffered on the cross for our sake.
An Altar Server should never be afraid to face small trials and difficulties, but rather offer these to God as penance for our sins.