Short answers, pulled from the story.
Norse sagas are prose stories and histories composed primarily in Iceland and to a lesser extent elsewhere in Scandinavia during the Middle Ages. They were written in Old Norse and its later descendants, chiefly Icelandic, rather than Latin, which was the dominant language of history-writing in medieval Europe.
The main genres are kings' sagas (konungasögur), sagas of Icelanders (Íslendingasögur), contemporary sagas (samtíðarsögur), legendary sagas (fornaldarsögur), chivalric sagas (riddarasögur), and saints' and bishops' sagas. Each genre covers distinct subject matter and time periods, from Scandinavian royal histories to translations of French chansons de geste.
Most sagas of Icelanders were written between 1190 and 1320. About two thirds of the medieval corpus of Íslendingasögur seem to have been composed in the thirteenth century, with the remainder in the fourteenth and fifteenth centuries. Some genres, particularly chivalric sagas, continued to be composed as late as the nineteenth century.
Scholars Gunnar Karlsson and Jesse Byock argued that the decentralized Icelandic Commonwealth created incentives for chieftains to document feuds and establish shared norms, while Iceland's remote location kept it beyond the reach of continental kings who might suppress subversive writing. Pragmatic factors including plentiful parchment from cattle farming and long winters also contributed.
The Age of the Sagas, called söguöld in Icelandic, refers to the period 930-1030, which is when most sagas of Icelanders are set. It spans roughly from the consolidation of settlement in Iceland through about a generation after the island's conversion to Christianity in the year 1000.
Writers who adapted saga narratives include J.R.R. Tolkien, Henrik Ibsen, Halldór Laxness, Henry Wadsworth Longfellow, Robert Louis Stevenson, August Strindberg, William Morris, and Laurent Binet, among many others. Snorri Sturluson is the medieval author most associated with the genre, probably having compiled and composed Heimskringla, the most prominent kings' saga.