A lot of what we know about the Middle Ages is due to archaeologists digging things up. Because the peasantry, the majority of the population, did not write things down, we know about them primarily through mentions in the records of people who did write things down (especially churchmen) and through archaeology. Preliterate people, like the Anglo-Saxons before about the seventh century, are also known mostly this way.
Villages can be reconstructed through archaeology, especially ones that were abandoned--and thus do not have modern villages built on top of them. With the population collapse of the fourteenth century, due to famine and the Black Death, many villages were permanently abandoned. They were silted over or fell into collapse or had their materials carted away for building elsewhere or were plowed over to make new fields. In England especially, low-flying planes have been able to see the outlines of old streets and houses under modern plowed fields, telling the archaeologists where to dig.
Archaeologists also dig up old cemeteries. It is possible, based on teeth and the relative proportion of head, torso, and limbs, to tell how old someone was when they died, as well as determine their sex from hip bones and pelvis. DNA from the bacterium of the plague (Black Death) has been recovered, allowing certainty as to what disease it actually was. Archaeologists can see if someone had a broken bone that healed, or a crushing skull wound that probably killed them, or a nasty leg infection that got into the bone and the like, thus revealing much about people's everyday lives.
Grave goods, the materials buried with someone, are also very interesting to archaeologists. A lot of warriors in late antiquity were buried with weapons. Stone sarcophagi carved with biblical scenes indicate that a population took Christianity seriously.
Archaeologists also dig up "midden" heaps, what one might also call garbage piles. One can tell, for example, if the local populace was eating beef if there are a lot of beef bones with gnaw marks. The presence of salt-water fish bones inland from the coast indicates that fish were traded by the coastal people. A lot of information about the medieval diet comes from these midden heaps.
Archaeologists will get very excited about a piece of pottery because there actually is very little in the midden heaps that is not outright garbage. In a pre-industrial age, people held onto their material possessions rather than throwing them away. Thus every shard that is discovered has meaning.
One has to wonder about archaeologists of the future digging up our landfills. They will find far more than they will know what to do with. Think about it the next time you open a gallon of milk or bottle of orange juice or container of cooking oil: there, under the screw cap, is a round piece of foil and/or plastic, manufactured for the sole purpose of being ripped off and thrown away. One wonders if the archaeologists of the future will decide they had a special ritual function.