What were the Dark Ages? What area of the world do they describe? When was this time?

Migration period, also called Dark Ages or Early Middle Ages, the early medieval period of western European history—specifically, the time (476–800 CE) when there was no Roman (or Holy Roman) emperor in the West or, more generally, the period between about 500 and 1000, which was marked by frequent warfare and a virtual disappearance of urban life.

The "Dark Ages" is a historical periodization traditionally referring to the Early Middle Ages or Middle Ages, that asserts that a demographic, cultural, and economic deterioration occurred in Western Europe following the decline of the Roman Empire.The term 'The Dark Ages' refers to the period between the fall of the Roman Empire and the Renaissance: the 5th – 14th centuries. It has been suggested that this period saw little scientific and cultural advancement.

The "Dark Ages" is a historical periodization traditionally referring to the Early Middle Ages or Middle Ages, that highlights the period of demographic, cultural, and economic deterioration that occured in Western Europe following the decline of the Roman Empire

The term 'The Dark Ages' refers to the period between the fall of the Roman Empire and the Renaissance: the 5th – 14th centuries. It has been suggested that this period saw little scientific and cultural advancement. However, the term doesn't stand up to much scrutiny – and many medieval historians have dismissed it.

d. migration