Short answers, pulled from the story.
The Gallic Wars were a conflict waged between 58 and 50 BC by the Roman general Julius Caesar against the peoples of Gaul, in present-day France, Belgium, and Switzerland. The wars ended with the expansion of the Roman Republic over the whole of Gaul.
Caesar portrayed the invasion as a preemptive and defensive action, but historians agree he fought primarily to boost his political career and to pay off significant debts incurred as consul in 59 BC. His own ambition was to conquer and plunder territory to get himself out of debt.
Vercingetorix was the charismatic king of the Arverni tribe who assembled an unprecedented grand coalition of Gauls and led a major revolt in 52 BC. After surrendering at the siege of Alesia, he was held prisoner for six years, then paraded through Rome and ceremonially garroted at the Tullianum in 46 BC.
At the Battle of Alesia in 52 BC, Caesar besieged Vercingetorix and his 70,000 to 100,000 warriors behind some 25 miles of fortifications built over a month. When both the defenders and a relieving army failed to break the Roman siege works, the relieving army melted away and Vercingetorix surrendered.
Although the collective Gallic armies were as strong as the Roman forces, internal divisions among the Gallic tribes eased victory for Caesar. Vercingetorix's attempt to unite the Gauls under a single banner came too late.
Caesar described the wars in his book Commentarii de Bello Gallico, the primary source for the conflict, but modern historians consider it propaganda prone to exaggeration. He made implausible claims about Gauls killed, including over a million total and 430,000 in a single camp, while claiming almost zero Roman casualties.