Short answers, pulled from the story.
Julius Caesar conducted his campaigns in Gaul from 58 to 51 BC. He captured the Gaulish resistance leader Vercingetorix in September 52 BC at the Battle of Alesia, which ended the majority of Gallic resistance to Rome.
Ancient Gaul covered 494,000 square kilometers, encompassing present-day France, Belgium, Luxembourg, and parts of Switzerland, the Netherlands, Germany, and northern Italy. It was first clearly described by the Romans.
Druids were the religious leaders of Gaulish society, presiding over sacrifices in wooded groves and maintaining the agricultural calendar and seasonal festivals. They also educated the aristocracy, claimed the power to decide questions of war and peace, and refused to commit Celtic oral literature to writing, which contributed to the eventual disappearance of the Celtic language from most of Gaul.
As many as one million people died during the Gallic Wars, roughly one in twelve of the Gaulish population. Another million were enslaved, 300 clans were subjugated, and 800 cities were destroyed. The entire population of Avaricum, some 40,000 people, was slaughtered.
The English word Gaul derives from the French Gaule, which comes from the Old Frankish term meaning Land of the Foreigners or Romans. It shares its root with the names Wales, Cornwall, Wallonia, and Wallachia, and is not related to the Latin Gallia despite appearing similar.
The Gaulish language survived into the 6th century and coexisted with Latin long enough to shape the Vulgar Latin dialects that evolved into French. Evidence survives in graffiti showing sound changes that matched earlier shifts in Gaulish, and the Vulgar Latin of northern Gaul eventually produced the langues d'oil group, which includes French.