This is from a book I'm reading:

The word “feudalism” comes from the Latin feuda, translated as “fief”, which means a piece land held in exchange for service to a lord. Feudalism, in the sense of the widespread division of the land into fiefs, is a common phenomenon in many lands in time of invasion or social decline. But the term was invented to describe the particular socio-political organisation of Western Europe in the later Middle Ages. It arose as a defensive reaction to the Viking invasions of the ninth century, and the breakdown in central authority which they caused. The breakdown was worst in West Francia, modern France, where royal authority almost disappeared. One result was serfdom: the lands which had belonged to the crown, the royal “fisc”, were given to local landowners, both ecclesiastical and lay, and the peasants who had cultivated the land, deprived of any protection from the crown, threw themselves on the mercy of the local landowners, bartering their and their children’s labour in return for protection. The second was feudalism proper: the freemen became vassals of lords, swearing to fight the lord’s battles in exchange for protection. A vassal was a knight – that is, he owned arms and a horse and was able to fight. Since this required money, he very likely owned land – either inherited, “allodial” land, or a “benefice” or “fief” granted temporarily, in the vassal’s lifetime only. A vassal might himself have vassals. Thus many of the king’s counts, or local officials, were at the same time both feudal lords and vassals of the king.

Feudalism ate into the king’s power in two ways: first, the kings’ peasants hardly counted as his subjects any more since their real masters were now their landowners; and secondly, the king’s vassals tended to leave his service for that of the most powerful local feudal lord. The king did not always resist this process, but rather reinforced it, since he saw that the feudal lord was the only guarantee of law and order in the countryside. Thus in the capitulary of Meersen in 847 King Charles the Bald ordered all free men to choose a lord, and likewise forbade them to leave their lord without just reason – which effectively made the bond of vassalage permanent in all normal cases. Again, in a capitulary issued at Thionville, he gave official recognition to the vassal’s oath, which thereby replaced the oath of allegiance as the main glue holding society together. Finally, in the capitulary of Kiersy in 877, Charles sanctioned hereditary succession to counties and other fiefs, which meant that county administration became hereditary and passed out of the king’s control.[456]

As a defensive system to preserve a minimum of order in a time of foreign invasion, feudalism undoubtedly had merits. But it was evidently much inferior not only to Byzantine-style autocracy, but also to the Carolingian system that preceded it. Moreover, as the threat of invasion passed, and feudalism spread from its homeland in Northern France throughout Western Europe in the eleventh century, its degrading and coarsening effect on general morality, and its potential, in certain circumstances, for a more-than-local despotism, became more obvious.

The author contrasts the Byzantine economy with Feudalism. How were things different in the Byzantine Empire?