Through the Constitution of the United States, every person in the country has the right to worship as he or she chooses. Every person is free to engage in whatever religious beliefs they find work for them. There are many, many Christian religions, many different sects of Christianity, each with their own unique worship. While all Christian religions believe in Christ, as opposed to the Jewish religion who believe they are still awaiting their Savior, each religion has different worship practices. Most Christian religions use communion. This is a place in their worship ceremony that mimics The Last Supper. In most Christian religions, there is a plate of bread passed around, as well as a cup, or individual cups of wine. For most Christians, these represent the body and blood of Christ that was shared at the Last Supper.
For Catholics their belief takes this to a higher level. In the Catholic religion, during the Consecration, the priest has the power to change the bread into the Body of Christ and the wine into the Blood of Christ. This process is called transubstantiation. The Catholic religion is the only Christian religion to practice this. They believe that the bread and wine become the Body and Blood of Christ. This is why the Catholic religion does not participate in the communion of other Christian religions, as these religions use their bread and wine as symbols only. While they are constantly seeking for full communion with all Christians, they believe that they should only receive communion as the Body and the Blood of Christ. When Christians attend other Christian ceremonies, they do partake of the passing of the bread and wine. When a priest takes his final vows, he is given this power, to perform transubstantiation during the Consecration of the Body and Blood at Mass.
This is another way in which all Christian religions, while sharing many of the same beliefs, have their differences to set them apart from one another.