Short answers, pulled from the story.
The Primary Chronicle, also known by its Russian title Povest' vremennykh let, is a chronicle of Kievan Rus' covering roughly 850 to 1110. It was likely compiled in the Kiev area in the 1110s and is considered the fundamental source for the earliest history of the East Slavic peoples.
Authorship is disputed. The text was long attributed to the monk Nestor, who lived from around 1056 to 1114, but modern scholars have concluded he was not the author because his known works contradict the Chronicle's internal evidence. A more likely candidate is Sylvester of Kiev, hegumen of St. Michael's Monastery in Vydubychi, who appended his name at the end of the Laurentian text in 1116.
Six main manuscripts are studied by scholars: the Laurentian Codex (1377), the Hypatian Codex (around 1425), the Radziwiłł Chronicle (around 1500), the Academic Chronicle (around 1500), the Khlebnikov Codex (around 1575), and the Trinity Chronicle (around 1450). Some scholars count only five main witnesses and exclude the Trinity Chronicle.
Its reliability is widely questioned. Scholars including Aleksey Shakhmatov, Dmitry Likhachov, and Ukrainian historian Oleksiy Tolochko have identified internal contradictions, dates that conflict with Byzantine sources, and passages that appear politically motivated or directly borrowed from religious texts. It remains indispensable because no other written source covers the same period, but it is used alongside critical correctives from the Novgorod First Chronicle.
The Laurentian text states that Byzantine emperor Michael III began his reign in 852, but Byzantine sources place his accession on the 21st of January 842. Aleksey Shakhmatov traced the error to a miscalculation in the Short History of Nikephoros I of Constantinople. The Chronicle then creates a second internal contradiction by calculating a different accession date of 860 a few sentences later.
The Chronicle drew on the Chronographikon Syntomon of Patriarch Nikephoros I, the Byzantine annals of John Malalas (a 563 work), the annals of George Hamartolus, traditional East Slavic oral epic poems called byliny, Norse sagas, Greek religious texts, and Rus'-Byzantine treaties. Russian philologist Aleksey Shakhmatov's 1908 analysis demonstrated that the text is an amalgamation of several ancestor accounts rather than a single literary composition.