The "Middle Ages" came after Rome, and before modern times.
But when, exactly, was that? The closer you look, the harder it is to
say. Someone studying the rural economy and the life of the peasantry might
find typically "medieval" features appearing as early as the 200s
AD, while someone interested in intellectual and political structures says
Roman models predominated in the west as late as the 900's, despite the
fall of the Empire. Determining when precisely the medieval gave way to
the "modern" is equally difficult. The best we can do to generalize,
perhaps, is to be arbitrary. So we can say the Middle Ages occupied the
centuries 500-1500, more or less.
That's a thousand years, in which a lot of changes took place. In 500
Christianity still belonged mostly to the cities and the Mediterranean rim.
The spread of the faith and the growth of the Church had enormous consequences
for all aspects of European society which can hardly be overstated. From
the breakdown of Roman power emerged many new political entities, which
eventually gave birth to powerful royal governments, and ultimately the
nation-states of the modern world. The population of 500 was small and declining,
most of it huddled in tiny pockets of habitation and farming separated from
each other by dark, dangerous forest and waste. But after 1000 the birth
rate soared, trade expanded, cities grew and prospered, and a dynamic, innovative,
self-confident culture began to spread its wings as never before. Even the
disasters of the late Middle Ages (of which the Black Death is the most
famous) proved only a temporary setback to Europe's growth.