Life in Medieval times became dark and miserable for many people. People lived somewhere on the continent of Europe. You've probably heard of many of these modern day countries: France, Italy, Spain, England, Germany. Each area had its' own king who ruled a large "kingdom" and the subjects or people served him and his family.
The geography of Europe was helpful to all these kingdoms. Many mountains provided natural barriers and safety. The many rivers provided food, fresh water, and travel. The continent of Europe forms a peninsula which made for easy trade with others. A peninsula has land with water on three sides. There are also many smaller peninsulas on the continent of Europe.
The most fertile land was the North European Plain and lots of farming was done here. Many places across the continent had fertile areas to farm though. The climate was seasonal and the Gulf Stream brought warm ocean currents across the Atlantic Ocean. During the Middle Ages, forests covered the land, but most of the trees have been cleared now.
Families were starving and disease had spread at the end of the Roman empire. It was also dangerous. Invaders took over cities as soon as the Roman Legion (Army) gave up. Because of all the problems, aqueducts dried up or were clogged and no fresh water was available. People fled to the countryside to find a better life. Here they started subsistence farming which is growing only enough food for your small village or family to survive. Building an empire again was not a concern, people were only concerned with survival and starting smaller kingdoms which would be easier to control.