Feudalism

The word feudalism characterizes a form of government and class hierarchy with land-owning nobles providing military and financial power and various resources to a higher noble or to a monarch in exchange for protection while requiring service from the knights and peasants within their domain.

People did not use the term "feudalism" in the Middle Ages, but in the 18th century, as people began to theorize about history, the concepts of the "fief" and "feudal system" were popularised by the likes of Giambattista Vico and Adam Smith, before becoming a part of Marxist theories of history. The word "feudalism" originated in French in 1823 and soon spread into other European languages.

How the system worked
The traditional feudal system was most common in Europe from the 9th to the 14th century CE. Kings in the early period were, by and large, warriors who had stolen land from other warriors. To maintain the land, they would provide a fief to any warrior willing to support the king in his ongoing battles. Those lands were further broken down into fiefs held by other nobles, or knighthoods, each knight being duty-bound to the king. In some areas of Europe, the land was plotted and leased for individual serf homes, though the leases were generally so exorbitant that no serf would ever be free of his indebtedness to the landowner. Serfs were never considered to "own" the land (more like the other way around).

Decline
In England, feudalism declined in the 16th century and was abolished in 1662; in the 17th century in western Europe, feudalism was replaced by the concept of absolute monarchy and the Divine Right of Kings (under leaders like James I of England and Louis XIV of France), in which kings had all the power and could exercise it directly, so not much of an improvement then. Meanwhile, early capitalism replaced the feudal economic system. The last vestiges of feudalism in western Europe were thankfully swept away by reforms instituted in the wake of the French Revolution.

Feudalism was great!
Some people have promoted the idea that life as a peasant in a feudal society was pretty great. Part of this goes back to the economist Juliet Schor who supposedly calculated that peasants only had to work around 150 days a year.

However, others have contested this. In particular, Tim Worstall has argued that Schor only counted labor owed to feudal masters and ignored the effort a peasant put in to grow food, make clothes, and do other basic domestic tasks necessary for survival. It depends on what you count as "work" but may reflect a systematic devaluing of domestic labor; domestic tasks are much easier in the modern western home now than in the middle ages, and hence a feudal peasant might have to spend much longer on them (to some extent they could avoid this by not washing their clothes ever, but they'd still have to cook and do other tasks that are seldom done today, such as making and repairing clothes, churning butter, etc.).

It is also sometimes said that medieval peasants ate better than today. GP Roger Henderson claimed they had a healthy diet of bread, 8 oz (227 grams) of meat and fish, beans, turnips, parsnips, and three pints of mild ale a day. Similarly to the paleo diet, such claims may be taken with a pinch of salt. They might have exercised more and consumed less sugar, but also died far younger, with little protection against food poisoning, parasites, etc., and it's not clear how many vitamins and minerals they'd get (especially as Henderson's diet seems to omit green vegetables or fruit). It would also have been dull and rather unappetizing, with little flavor (some herbs grew wild, but salt was expensive for most people, and other flavorings also hard to obtain). While there is debate over safe levels of alcohol consumption, 3 pints a day would exceed most recommendations.

Non-European use of the term
Pre-modern Japan is often analogized as a "feudal society" to show some similarities with the European Middle Ages, but the correlation is illustrative at best and fails to really describe the true situation in Japan.

Scholars have said that Ancient Egypt also had a feudal-like system, though the true obligation was a religious duty as the king in any Egyptian society was bound to the people through his role as "God" of the people.

While feudalism faded out of use in Europe during the late Middle Ages, similar systems in other countries survived much later. The Russian emancipation of the serfs took place in 1861, and Japan's hierarchy of farmers, samurai, and daimyo (lords) under the ruling Shogun was abolished after the Meiji Restoration of 1867.

Individuals in mainland China generally adopt the Marxist use of the term and refer to all Chinese history under monarchies (or warlords 1912-1949) as "feudalism" (half-feudalism/half-colonial after the Opium War), even though European-style feudalism was largely over in China by the Qin dynasty, which began ca. 221 BCE.