Short answers, pulled from the story.
Pliny the Younger was a Roman lawyer, author, and magistrate born in Novum Comum (modern Como) around 61 AD. He is best known for his 247 surviving letters, which include eyewitness accounts of the 79 AD eruption of Mount Vesuvius and the earliest surviving Roman documents to mention early Christians.
Pliny the Elder died during the eruption of Mount Vesuvius on the 24th of August or October 79 AD while attempting to rescue his friend Rectina. Pliny the Younger described these events in two letters written for the historian Tacitus roughly 25 years after the event, letters now known as Epistulae VI.16 and VI.20.
Volcanologists named this type of eruption after Pliny the Younger because his two letters describing the 79 AD Vesuvius eruption contain such precise physical observations that modern scientists use them to classify eruptions of that character. The letters were written to the historian Tacitus approximately 25 years after the event.
Around 112 AD, while serving as governor of Bithynia-Pontus, Pliny wrote Epistulae X.96 to Emperor Trajan describing how he had been conducting trials of suspected Christians accused anonymously and asking for guidance on how to treat them. His letter and Trajan's reply are the earliest surviving Roman documents to refer to early Christians.
Pliny rose through the full Roman cursus honorum, serving as Quaestor in his late twenties, Tribune of the People in 91 AD, Praetor in 93, Prefect of the military treasury from 94 to 96, Suffect consul in 100, and finally imperial governor of Bithynia et Pontus around 110 AD.
Pliny the Younger wrote 369 letters in total, of which 247 survived. The first edition of his Epistles was published in Italy in 1471, and the first complete edition was produced by the press of Aldus Manutius in 1508.