We are singing the Offertory chant which shows our unity and shows that we are praising God. The faithful are waiting for the ushers to come around with the baskets for the collection. This is actually a gesture with great spiritual significance. St. Justin Martyr talked about the importance of taking up a collection on the Lord's day. Certainly it shows we are supporting the operations of the parish, but it also shows we are supporting the poor and needy. In ancient times, people would have brought the produce from their land, thus showing that their support for the parish comes from their own toil. Nowadays, the monetary collection shows the exact same thing.
Also at this time, the bread and wine are brought forward. There is profound spiritual significance here. It should be noted that they are brought forth by the people from the people. Moreover, it takes hard work and patience to make bread and wine. It shows that human beings can take the fruits of the earth, which are God's gifts, and with human ingenuity, also God's gift, offer them back to Him. We should also notice these are the exact same elements Jesus used at the Last Supper.
The Prayerful opportunity continues. We know what is going to happen to the bread and wine. They will be consecrated, made holy, set apart. We know God will change them into the Body and Blood of Christ, using the priest as His instrument. We further know that they will be offered to the Father. As the bread and wine are brought forward to become our offering, we are invited to offer ourselves with them to the Father. We can prayerfully place ourselves on the altar with the bread and wine: our hopes, dreams, desires, sufferings, joys, talents and all that we are, to become an offering to the Father.
It is also appropriate, as much as possible, to have one vessel for bread, signifying the one loaf; and one chalice of wine, further signifying our unity in Christ. Individual cups would greatly diminish the idea of unity in Christ.
At this point of Mass, the altar has become the centerpiece and focal point. It is a symbol of Christ, and it is set apart for one specific purpose, nothing else. The priest can incense the altar along with the cross and the bread and wine. The General Instruction on the Roman Missal (GIRM) states that this is "to signify the Church's offering and prayer rising like incense in the sight of God."
The GIRM continues: "Next, the priest, because of his sacred ministry, and the people, by reason of their baptismal dignity, may be incensed by the deacon or another minister." This reminds the faithful that by virtue of our baptism, we are set apart to be God's own. We are consecrated to Him.