Final answer:
The screen or partition in question is called a templon, which evolved into the iconostasis commonly found in Orthodox churches, marked by intercolumnar icons.
Step-by-step explanation:
The screen or partition that separates the bema from the nave of an eastern church is known as a templon. Initially, it consisted of chancel slabs, colonnettes, and an epistyle or templon beam, allowing laypeople to view the clergy around the altar. Over time, it evolved into the iconostasis, which is characterized by the presence of intercolumnar icons and can still be seen in Orthodox churches today. The bema itself is adorned with frescoes and mosaic images that reflect its sacred role in the celebration of the Eucharist, illustrating a deep connection to the religious practices and beliefs of the time.