The Middle Ages was a time in European history roughly between the 5th Century and the 15th Century CE when vast majority of Europe was run by a feudal system with lords and vassals. The Middle Ages are also referred to as the Dark Ages and the Medieval times. The exact time of the Middle Ages varied between different European countries. The Middle Ages ended with the Renaissance.
There was little scientific and intellectual progress during the Middle Ages in the Western World (the Eastern World and the Islamic World was flourishing at the time). In Europe, except for tolerant Poland, numerous intellectuals (Jan Hus, Jerome of Prague) who dared question the Roman Catholic Church were burned at the stake. The Dark Ages are what happens when Conservative Christians are allowed to rule.
The Medieval Period, is a Dark Period. Poverty was plenty, the Church was in full power. It happened after the fall of Rome. The old colosseum, was slowly being taken over by animals. Christianity was the dominant religion. But, in the later Middle Ages, science and philosophy was slowly taking over. William of Ockham, created Ockam's Razor, which states, the idea with fewer notions is more likely to be true. St. Gregory invented the Gregorian Calender. But, science was suppressed, anyone with ideas that contradicted the beliefs of the Church, was to be burnt at the stake.
Rational Evolution (1930)
The Dark Ages (documentary)