The idea that the Middle Ages were "dark ages" has been exaggerated a lot. In fact the Middle ages are split into three distinct time periods, which were all quite different from each other. There are the Early, High, and Late Middle Ages. Despite the reputation for being a time when there were no moves forward in Europe, there were actually many important achievements. .
The Middle Ages lasted from about 500-1500, the time between the end of the Roman Empire and the Renaissance. The Early Middle Ages were probably the time that most fits the term Dark Ages, even though even they weren't all bad. .
Christianity spread a lot throughout Europe during this time, thanks in part to rulers like Charlemagne and Clovis who converted whole lands. But while many people were Christian by name, and the pagan religions were dying out, most people didn't practice it. One reason for this is that hardly anyone was literate, so they couldn't read the Bible. Most clergy of the time were even illiterate, and led very secular lives. It was a disgraceful time for the Church, because there was a lot of corruption, such as priests who lived with women and bought their positions. .
The economic life for most Western Europeans was not much better than the religious and intellectual quality. There weren't really any great cities and most common people worked in agriculture to provide what they could to keep their families alive. .
However, in the eighth century Charlemagne succeeded in starting a small renaissance and uniting much of the Frankish territory. He preserved some of the Latin literature that might've otherwise been lost and started a few schools to educate monks. Even though the empire fell apart after the death of Charlemagne and Europe once again regressed to an unstable period, it had given a sense of unity to the people and had managed to spread Christianity and some intellectual achievements that lasted until the High Middle Ages when they were renewed again.