#2
The ambo was in the middle of the nave and elevated so the human voice (singing and reading) could be heard by all without electronic amplification. The Liturgy of the Word was entirely centred around the ambo, with the people, standing, facing it from all directions. 

The Little Entrance was a procession from the sanctuary with the Gospel Book to the ambo. For the Eucharistic Liturgy, the people move towards and faced the altar in the middle of the sanctuary. The purpose of this low barrier was, obviously, to demarcate the area of the people and prevent crowding into the area reserved for the Eucharistic action. 

The Great Entrance was a procession from the back vestibule where the deacons, prior to the public liturgy, had collected the bread and wine brought by the people and selected what was required for the Eucharist. This procession, having gone around the ambo, followed the runway from the ambo to the sanctuary.