Short answers, pulled from the story.
The Library of Alexandria was one of the largest and most significant libraries of the ancient world, located in Alexandria, Egypt. It formed part of a larger research institution called the Mouseion, which was dedicated to the Muses, the nine goddesses of the arts.
The idea of a universal library may have been proposed by Demetrius of Phalerum, an exiled Athenian statesman, to Ptolemy I Soter. The library itself was probably not built as a physical institution until the reign of his son, Ptolemy II Philadelphus.
The exact number is unknown, with estimates ranging from 40,000 to 700,000 scrolls at its height. King Ptolemy II Philadelphus is said to have set 500,000 scrolls as an objective for the library.
Scholars at the Library included Zenodotus of Ephesus, Callimachus, who wrote the Pinakes, Apollonius of Rhodes, author of the Argonautica, Eratosthenes of Cyrene, who calculated the earth's circumference, Aristophanes of Byzantium, and Aristarchus of Samothrace. Hero of Alexandria, who invented the first recorded steam engine, also worked there.
Its destruction came gradually over several centuries. Julius Caesar accidentally burned part of the collection in 48 BC, a Palmyrene invasion and imperial counterattack between 270 and 275 AD probably destroyed whatever remained, and the daughter library in the Serapeum was demolished in 391 AD under a decree by bishop Theophilus of Alexandria.
Julius Caesar set fire to Egyptian ships during his civil war in 48 BC, and the flames spread to parts of the city. Seneca the Younger quotes Livy as saying the fire destroyed 40,000 scrolls, but it is unclear how much was actually destroyed, and the Library seems to have either survived or been rebuilt shortly afterward.
The Bibliotheca Alexandrina is a modern library and cultural center in Alexandria, Egypt, completed in 2002 to commemorate the original Library of Alexandria. The idea of reviving the ancient library was first proposed in 1974, and the building was designed by the Norwegian architectural firm Snohetta.