The year was the Roman Empire's first civil war, and it marked the change from the first imperial dynasty, the Julio-Claudians, to the Flavians.
Based on Wikipedia: Year of the Four Emperors
The Year of the Four Emperors, AD 69, was the first civil war of the Roman Empire, during which four emperors ruled in succession, Galba, Otho, Vitellius, and Vespasian.
It is considered an important interval, marking the change from the Julio-Claudians, the first imperial dynasty, to the Flavian dynasty.