During the singing of the Lamb of God at Mass, the priest is breaking the large host into smaller pieces. This is to symbolize how we, though many, are receiving from the One Bread, the same Body of Christ. In the earliest days of the Church, the eucharist or Mass was known as "the breaking of the bread." At the end of the gospel today, we are told that the disciples recognized Jesus in the breaking of the bread. When he "broke bread" with them, they remembered how he did the same at the Last Supper.
When Mass was in Latin, the priest ended it by saying "Ite, missa est." That means, "Go, the Mass is ended." "Ite" means "go" and "missa" means "to be dismissed." This is where we get the word "Mass." In the Roman Missal, the priest has 4 options for the dismissal of the people after the final blessing. They all begin with the word, "Go": Go forth, the Mass is ended. Go and announce the gospel of the Lord. Go in peace, glorifying the Lord with your life. Go in peace.
We are not just announcing the end of Mass, but telling people to go from there in order to live the faith they just celebrated. Go and glorify the Lord with your life. Go and live in peace. Go and announce the gospel by the way you live. We are sent on a mission to bring our faith into daily life