Period of time that fits in between the very late Roman period (when the whole of Europe - except a few hairy, uncouth bits - was civilized and threw Christians to the Lions) and the Renaissance - the rediscovery of all the stuff that had been lost when the Vikings stole or burned it down. Let's call it 800AD till 1400AD.
During this time the feudal system was created. Here you had a liege (lord) who taxed your ass but promised to protect you from anyone else who might try to tax your ass. Someone bigger and tougher was his lord to whom he paid part of your taxes and so on up to the King (who in theory was the baddest ass). Think pyramid selling with violence and major intimidation OR even as protection money.
According to the Norman way of thinking, your lord (allegedly) had a thing called Droit de Seigneur (the right of the lord) which meant he could boff your virgin daughter if he fancied a bit. Not many virgins around during this period - a bit like Liverpool.
During this period Jews were persecuted [No change there then? ... Jews are ALWAYS persecuted!], Muslims and Christians fought The Crusades and Jihad. The rulers of the European nations were corrupt megalomaniacs who fought wars on a whim and were out for personal enrichment and their legacies. The people thus suffered mightily though taxes, plagues and poor government. Some things never change!
The nailsest of the nailsest during this time was the knight. Forerunner of the Chally 2, this was a man wrapped in plate steel, mounted on a semi-insane herbivore, given a large stick with a spike on the end and sent (en masse) screaming into groups of prototype squaddies with the aim of proving their body armour sucked. This lasted till the proto-squaddies started using the L1A1 Longbow (a device for archery, not the helicopter) to render a shoeing to the Knights while they were still 200 yards away. Six hundred years later, still not much has changed.
Religious 'schisms' took off in great number during this time resulting in the horrible persecution of all manner of inoffensive and well meaning (but obviously simple in the head) people by the Holy Church of Rome. Religious wars were a growth industry. It's amazing that Christianity survived - although all flavours of Christians could get together to shoe the odd Muslim or two.
Plague depopulated vast parts of the medieval world. This was caused by NHS cleaners not washing their hands properly ... or maybe a Goose caught a cold and sneezed on a peasant who was a bit poorly. Other theories include fleas from Oriental rats passing on something nasty. No matter what caused it, it's estimated that a quarter of England's population died of plague in the 14th century.
So with death taken care of, lets move onto that other certainty ... taxes! Your average Medieval serf paid an effective tax rate of 33.3% and was considered effectively a slave. In other words his tax freedom day was the 122nd day of the year. Your current peasant's tax free day as he toils under Nu-Labour's very taxing policies is the 3rd June ... the 154th day of the year and remember the medieval peasant didn't have Gordon F'ing Brown's stealth taxes to contend with. Welcome to slavery!
Japanese society during this time was extremely stratified. If you were born into a mercantile family... you were a merchant. NO choice. Same with being a peasant or Samurai. The Emperor was a God on Earth, although the country's military warlord (Shogun) was the real power behind the throne.
Military development stopped in the 1700s, thus swords (the famed Katana), spears and muskets were the weapons still in use when the (fresh from the Civil War) Spams turned up. Queue one shoeing! Go watch the Tom Cruise movie Dances with Ninja for details of how pointless a war this would have been.
Japanese society was still under the control of the Samurai at this time. If you (as a peasant) did not show due reverence to a passing Samurai, he had the right to kill you there and then. Surrendering enemy troops were considered to no longer care about their cause and were despised/mistreated as a result. This casual brutality endemic in Japanese society resulted in the incidents of brutality to POWs in WW2. Oddly, and in stark contrast, captive Germans during the Great War were treated very well.
Sort of exactly like it is just now with sod all amenities, poor sanitation, rampant poverty, a bunch of homicidal maniacs running about, religious nutters in charge and a population 3 seconds away from declaring Holy War on our collective arrse... But without the fully automatic weapons, IED's, nuclear ambitions and Al Jazeera TV telling the west what a bunch of barstewards we all are.
It was however still Sunni and Shi'ite.
The United States of America
did not exist at this time ... take a moment to imagine a world without Spams. Peaceful isn't it.
South America had extremely well organized and technically advanced societies while us First Worlders where still wondering was the toilet a good idea or should we just continue to shit in the gutter. Aztecs, Mayans and, Incas all had extremely effective societies till the Spanish turned up and shoed them into the stone age.
Pretty much the same as it was 500 years before and after everyone else's medieval period. Highly sophisticated but with a stratified society that you couldnt dent with a feck off horde of armed maniacs. Invaders like the Mongols came, kicked in some back doors, got absorbed (corrupted by luxury) and vanished into the general population but the ruling dynasties rumbled on through the centuries.
Exceedingly cunning when it came to making things out of virtually nothing. Soup from bits of sharks no one wanted or even birds nests; clothes from the bottoms of silkworms; money from an exciting new concept called tax; absolute rulers who trough it up at the peasants expense ... medieval China gave us much of what we take for granted today.
Will add more later.
FB adds: - also known for folk being quite horrid to each other at times, often with pointy bits of metal or hot branding irons. This has led to "medieval" being used as a verbal shorthand for overly-violent, as heard in the film Pulp Fiction by Quentin Taranteatime (shall I be motherfucker?) when the Ving Rhames character is heard to suggest that he will get some of his focus group facilitators to "... get medieval on yo' ass!". One suggests this means they would resort to some unpleasantness as opposed to dance in a courtly manner to Greensleeves.
RH: It should be noted that Morris Dancing is fairly medieval in both senses of the word!