Q. 1. What is the purpose of the "Altar Bread?"

A. 1. The "Altar Bread" is also known as the element, the wafer, the loaf in non-Catholic faiths, the host, the Consecrated Host, the Eucharist, the Holy Eucharist, the Communion, the Holy Communion and the Sacramental Bread.

During the celebration of the Holy Mass, the Altar Bread is consecrated by the ordained priest of the Catholic Church, at which time the Bread (Host) becomes the Body of Christ. Equally, during the consecration of the elements, the consecrated wine becomes the Blood of Christ.

The Consecration of the Bread is the fulfillment of Old Testament prophesies whereas God promised to make His dwelling among His people.

"See, I am sending my messenger to prepare the way before me, and the Lord whom you seek will suddenly come to his temple. The messenger of the covenant in whom you delight—indeed, he is coming, says the Lord of hosts. But who can endure the day of his coming, and who can stand when he appears? For he is like a refiner’s fire and like fullers’ soap." [Malachi 3:1-2]

Through the Holy Eucharist, the Real Presence of Christ on earth, the above prophesy was fulfilled.

The word "host" is derived from the Latin hostia, which means "sacrificial victim". The term can be used to describe the bread both before and after consecration, though it is more correct to use it after consecration. Prior to consecration, the term "altar bread" is preferred. The sacrifice of Jesus according to Christian theology puts an end to the need for animal sacrifice as had been practiced in the Jerusalem Temple and all blood sacrifice once-for-all. However the word was retained to describe the bread of Eucharist as a liturgical representation of the Christ's sacrifice.

The hostia or sacramental bread, may be made out of only four ingredients: fine (white) wheat flour, pure water, yeast, and salt. Sometimes holy water will be either sprinkled into the dough or on the kneading trough at the beginning of the process.

[Source: https://en.wikipedia.org/wiki/Sacramental_bread]

The Catholic Church teaches that the Real Presence of Jesus dwells in every particle of the Consecrated Bread. During Holy Communion, you receive the fullness of the Body of Christ in both, the complete Consecrate Host or a portion of it.