Short answers, pulled from the story.
The physical medium was animal skin prepared for writing. Writers in Iceland used Old Icelandic, a western dialect of Old Norse to record these stories.
Sigurður Nordal published Sagalitteraturen to organize the sagas into five chronological groups based on when they were written. His first group covers 1200 to 1230 and includes works dealing with skalds like Fóstbrœðra saga.
One saga, Egil's Saga, is believed by some scholars to have been written by Snorri Sturluson. Sigurður Nordal stated he became convinced it was the work of Snorri unless new arguments appeared.
The standard modern edition of Icelandic sagas is produced by Hið íslenzka fornritafélag, also called Íslenzk fornrit. The preservation efforts continue through this Old Icelandic Text Society which manages critical editions today.
Most events described took place within Iceland itself or involved its earliest settlers during the ninth, tenth, and early eleventh centuries. These narratives reflect the struggle and conflict that arose within societies of early generations of settlers.