Complex sentence: The Gallic Empire (in Latin "Imperium Galliarum") is the modern name for the independent realm that existed from 260 to 274, during the Roman Empire's Crisis of the Third Century.
Split into simpler sentences: The Gallic Empire (Latin: "Imperium Galliarum") is the modern name for a breakaway realm that existed from 260 to 274. It originated during the Roman Empire's Crisis of the Third Century.