The term 'Roman Galley' refers to two types of ships used by the Ancient Romans. The first is the TRIREME, which was a three-tiered ship with three banks of oars and a single mast. It was used for both military and commercial purposes and was the most common type of warship in the Mediterranean during the Classical period. The second type of Roman galley is the BIREME, which was a two-tiered ship with two banks of oars and a single mast. It was primarily used for military purposes and was the most common type of warship in the Mediterranean during the Hellenistic period.