You will notice that the priest kisses the altar upon entering and leaving the sanctuary. This occurs because in ancient Rome, during the time of the persecutions (link), Catholics celebrated Mass in the catacombs, which were burial grounds (a network or maze of tunnels in which the great martyrs were buried). They would celebrate Mass on the tombs of the martyrs; for those were the only altars they had. The priest would kiss the altar as a greeting to the dead person.

The Alb: This is the only purely liturgical garment. It is the white toga like gown. It represents the priestly vestment of Christ (seamless). The white garment is also a symbol of charity (Cf. The Parable of the Wedding Feast). It symbolizes our baptism, and it is an outward sign of our dignity as a member of the redeemed. During the baptismal rite, you are given the white garment and the priest or deacon says: “Bring that dignity unstained into the everlasting kingdom of God.”

The Stole : The scarf-like garment that priests wear—deacons wear a stole that slants from the left shoulder down to the right side. In Roman times, the magistrates (judges) wore a long scarf when they were engaged in their official duties. It was a sign of authority as well. The priest wears the stole when he is occupied with official priestly duties. Note also that the priest kisses the stole as he puts it on and removes it. The priest is asking God to grant him, on the last day, "the garment of immortality".

The Cincture: This is the chord that’s used to gird the Alb. It symbolizes the virtue of chastity required of a priest. It recalls the Scripture in which Jesus tells Peter: “In all truth I tell you, when you were young you put on your own belt and walked where you liked; but when you grow old you will stretch out your hands, and somebody else will put a belt round you and take you where you would rather not go.”

The Amice: (square piece of white cloth that’s wrapped around the base of the neck and shoulders of the priest). In the Middle Ages it was worn by the priest to protect him from the cold when celebrating Mass in cold and damp Churches. It symbolizes “the helmet of salvation” (see Eph 6, 17) and the virtue of hope.

The Chasuble: The outer vestment worn by the priest. It was originally a poncho. Everybody in ancient Rome would wear a poncho, which would protect you from the elements at night. The priest's poncho or cloak would have an insignia on his, a cross, which would signify that he was the priest (since everyone wore these). He would not go out in public like that, mind you, for fear of persecution. The Chasuble, because of its weight, is a symbol of charity. The early ponchos were heavy, and so the Chasuble represents the yoke of unselfish service of the Lord.

In the Eastern rite, you will notice that communion falls in the center of the liturgy. But in the Roman rite, communion occurs at the end. The reasons for this are historical. During the time of the Roman persecutions, Christians were in hiding. They celebrated Mass in the catacombs. And so we were a Church “on the run”. In the early Church, they did what they had to do and then left. They’d confess, give glory to God, listen to the word, receive the Eucharist, receive the final blessing and then leave quickly. They did not unduly delay the liturgy; for the longer they lingered, the greater the chances they'd be found out. Their lives were at risk.

It is used four times during Mass, at the beginning, at the gospel, the preface of the Mass, and the final blessing. The roots of this greeting go back to Roman times. This was the typical greeting that Christians would receive and reciprocate during the time of the Roman persecutions. Christians would use the response “And also with you” as a codified language. It was a way to identify a person as a Christian. It was also a way to spot an infiltrator at a Mass; for he wouldn’t respond with “and also with you”, for he wouldn’t be familiar with the greeting. Greeting someone with “The Lord be with you” would be unintelligible to a Roman, but not entirely so. For there were many “lords” in Rome, and so the greeting would not be entirely out of place.

During Roman times, after the Creed was said and the prayers of the faithful, gifts would be brought up, such as bread and wine (which would be used for Mass), as wells as chickens, eggs, clothing, etc.,. The gifts would serve a two-fold purpose: a) celebration of Mass (bread and wine), and b) the needs of the priest and needs of the poor. This is where the "washing of the hands" comes from. We know that the priest washes his hands during the liturgy of the Eucharist, and he says: “Lord, wash away my iniquity and cleanse me from my sins.” The original purpose of this gesture was simply to wash his hands that became dirty from handling the gifts that were brought up, such as the chickens and other foods. Later it became a symbolic ritual that his heart would be clean.

Sanctus (Holy, holy, holy): There is significance in saying the “holy, holy, holy” three times. The three times signifies the superlative. Our superlative in modern English also follows three: good, better, best. The best is third, after good and better. Or, wise, wiser, wisest. In Scripture, the three is indicative of the superlative, in this case, the degree of holiness. Only God can be holy, holy, holy, that is, the fountain of all holiness.