Short answers, pulled from the story.
A Thing was a governing assembly of free people in early Germanic society, presided over by a lawspeaker who recited the law from memory. Things served as parliaments and courts at local, regional, and supra-regional levels, and also hosted social events, trade, and religious rites. Only free men of full age could participate in decision-making, according to Norway's Law of the Gulating.
The oldest written reference to a Thing is on a stone pillar found at Housesteads Roman Fort along Hadrian's Wall in Northumberland, dated between 43 and 410 CE. The inscription, raised by a Frisian auxiliary unit of the Roman army, dedicates an offering to Mars Thincsus, meaning the god Mars of the Thing.
In English, the word 'thing' is attested from 685 to 686 in the sense of 'assembly.' Before 899 it had shifted to mean a being, entity, or matter; by about 1000 it referred to an act or deed; and by around 1300 in Middle English it meant personal possessions, eventually becoming the modern sense of 'object.' The original meaning of 'meeting' did not survive the transition to Middle English.
The Icelandic Althing, held at Þingvellir, is considered the oldest surviving parliament in the world. It was a national assembly where thirty-nine goðis plus nine additional members formed the Lögrétta, or Law Council, which reviewed and created laws, set fines and punishments, and received word of sentences of outlawry. Unlike other medieval European societies, Iceland relied on the Althing's legislative and judicial institutions at the national level with no executive branch of government.
Iceland's Alþingi (General Thing), Denmark's Folketing (People's Thing), and Norway's Storting (Great Thing) all take their names directly from the old Germanic assembly. The legislatures of the Faroe Islands (Løgting), Åland (Lagting), Greenland (Landsting), and the Isle of Man (Tynwald, meaning Thing Meadow) also carry the word.
Thynghowe was a Danelaw meeting place in Sherwood Forest, Nottinghamshire, England, located in an area of old oaks known as the Birklands. Its location was lost to history and rediscovered in 2005 and 2006. English Heritage confirmed the site was documented under the name Thynghowe in both 1334 and 1609, and experts believe it may have marked the boundary between the kingdoms of Mercia and Northumbria.