The altar against the eastern wall (ad orientem) is a centuries old tradition full of significance. First it has the people facing east, the rising sun, which is a symbol of the resurrection of Christ. Second, east is also the symbolic direction of His Second Coming (Matthew 24:27). Third it connects the Church militant with the Church triumphant. We are to imagine the altar as the end of the heavenly banquet table, breaking into our time/space world. It is like the kiddie table at a Thanksgiving meal, where we are feasting together with all the faithful departed. Third, the eastward facing altar has the priest face the Lord rather than the people. That is important because his primary duty in worship is to minister to the Lord. The priest is not the host, he is the officiant, and so he leads by pointing the people to the Host.
I once had a Spanish speaking Bishop visit our church and through a translator asked me, “Do you celebrate with your back to the people?” I asked the translator to literally interpret my response. I said, “No sir I do not celebrate with my back to the people. I celebrate facing Christ with the people.” To this he gave a nod of understanding if not agreement.