Short answers, pulled from the story.
The Gauls were a group of Celtic peoples who inhabited mainland Europe during the Iron Age and Roman period, roughly the 5th century BC to the 5th century AD. Their homeland, called Gaul or Gallia, covered much of what is now France, Belgium, Switzerland, southern Germany, Austria, and the Czech Republic. They spoke Gaulish, a Continental Celtic language.
Julius Caesar launched the Gallic Wars in 58 BC and completed the conquest of Gaul by 51 BC. His motives included accumulating gold to pay off personal debts and securing a military triumph to advance his political career. So much gold was taken that the price of gold fell by as much as 20 percent after the war.
Gallic forces invaded Greece twice, in 279 BC and 278 BC, reaching Delphi before being repelled. Their leader Brennos was wounded at Delphi and died there. A surviving group crossed into Asia Minor in 278 BC after being invited by Nicomedes I of Bithynia, settling in central Anatolia and becoming known as Galatians. The Galatian language continued to be spoken in that region until the 6th century.
Druids were the priestly class who oversaw religious ceremonies, served as judges, acted as teachers, and kept oral tradition. Gaulish religion was polytheistic, with deities tied to thunder, craft, healing springs, and fertility. Druids held ceremonies in sacred groves called nemetons. There is also limited evidence, largely from Greco-Roman sources, that human sacrifice by burning in wicker structures was practiced.
Gaulish coexisted with Latin through the Roman period and may have survived in some French regions into the mid to late 6th century. It contributed loanwords, calques, sound changes, and influence on word order and conjugation to the Vulgar Latin dialects that became French. Computational research has found evidence that Gaulish also shifted the grammatical gender of some early French words to match the gender of corresponding Gaulish terms.
Genetic studies published between 2018 and 2022 examined individuals from La Tene burial sites in France. They found strong genetic continuity between Bronze Age and Iron Age populations in France, with significant steppe ancestry linked to the earlier Yamnaya, Corded Ware, and Bell Beaker cultures. Northern French samples showed genetic links to Great Britain and Sweden, while southern samples linked to Celtiberians. A 2024 study of Cenomani Cisalpine Gauls from Verona identified paternal lineages belonging to haplogroup I2a1b1a1b1 and subclades of R1b.