Short answers, pulled from the story.
Julius Caesar reported that the Galli called themselves Celtae within their own language. Modern scholars trace this term to the Celtic root Gal(a)-to- meaning power or capacity.
The La Tène culture arose during the 7th and 6th century BC under Mediterranean influence. This culture flourished from 450 BC until Roman conquest in the 1st century BC and spread as far east as southern Poland, Slovakia, and Hungary.
As many as one million people died during these wars representing about one in twelve of the total population. Another million were enslaved while three hundred clans were subjugated and eight hundred cities were destroyed including Avaricum which held forty thousand inhabitants.
Citizenship was granted to all inhabitants in 212 AD through the Constitutio Antoniniana. The region remained a province until AD 486 when the Domain of Soissons fell to the Franks.
Druids presided over human or animal sacrifices made in wooded groves or crude temples and preserved the annual agricultural calendar. They claimed authority to determine questions of war and peace internationally while monitoring ordinary religion and educating the aristocracy exclusively.