Short answers, pulled from the story.
The modern English word altar derives from the Latin altare, meaning burning place. This linguistic root reveals the object's primal function as a site of fire and transformation. The etymological connection to adolere, to burn, displaces the native Old English word wēofod.
The Hebrew Bible specifies that altars were typically made of earth or unwrought stone. These early altars rejected the use of cut stone to avoid the defilement of the altar by human tools. This emphasis on natural materials underscored the belief that the altar was a direct conduit to the divine.
After the sixth century the contrary orientation prevailed, with the entrance to the west and the altar at the east end. This shift allowed ministers and congregation to face east during the whole celebration. The Christian replication of the layout and the orientation of the Jerusalem Temple helped to dramatize the eschatological meaning attached to the sacrificial death of Jesus the High Priest.
A Holy Table in an Eastern Orthodox church typically has five legs. These include one leg at each corner plus a central pillar for holding the relics placed within it at its consecration. The altar is normally free-standing and about one meter high.
The carroccio was a four-wheeled mobile shrine pulled by oxen and sporting a flagpole and a bell. It served as the army standard and functioned as a mobile altar on which Mass was celebrated before a battle. Altar stones were used by army chaplains of the Latin Church in the period leading up to the 20th century.