Short answers, pulled from the story.
Plutarch was a Greek philosopher, biographer, and historian born before AD 50 in Chaeronea, a small town in the region of Boeotia. He is best known for the Parallel Lives, a series of paired biographies of illustrious Greeks and Romans, and for the Moralia, a collection of seventy-eight essays and speeches. He also served as a priest at the Temple of Apollo at Delphi.
The Parallel Lives pairs a biography of a notable Greek with a biography of a notable Roman, usually followed by a brief comparison of the two subjects. Plutarch's stated goal was to explore the influence of character on human lives and destinies rather than to write conventional history. The surviving text contains twenty-three pairs plus four unpaired single lives.
Shakespeare drew on Sir Thomas North's 1579 English translation of the Lives, which was itself based on Jacques Amyot's French translation of 1559 rather than the original Greek. Shakespeare paraphrased portions of North's translation in his plays and occasionally quoted from it verbatim.
Around AD 95, Plutarch became one of the two sanctuary priests at the Temple of Apollo at Delphi, a site that had declined since the classical Greek period. He also served as manager of the Amphictyonic League for at least five terms between 107 and 127, organizing the Pythian Games. A portrait bust was dedicated to him for his efforts in helping to revive the Delphic shrines.
The Moralia is a collection of seventy-eight essays and transcribed speeches by Plutarch on topics ranging from ancient Egyptian religion to moral philosophy and practical ethics. One essay on the appearance of the moon's surface became a source for Galileo. Montaigne's Essays contain more than four hundred references to Plutarch's Moralia and are consciously modelled on its discursive style.
Plutarch received Roman citizenship through the sponsorship of Lucius Mestrius Florus, an associate of the emperor Vespasian. The evidence is his new Latin name, Lucius Mestrius Plutarchus, which follows Roman naming conventions by incorporating his patron's family name. As a Roman citizen, Plutarch held the rank of the equestrian order.