A figure with one source
Everything known about Vercingetorix comes from Caesar's Gallic War, with brief later notices in authors dependent on it. He is the best-attested Gallic individual of the period and he is attested by the man who destroyed him, in a work written to justify that destruction to a Roman readership.
Caesar's portrait is not hostile, and the reason is worth noting: a formidable opponent makes a more impressive victory. Readers should weigh the flattery as carefully as they would weigh abuse.
The revolt
In 52 BCE, with Caesar wintering in Italy, a coordinated rising broke out across Gaul. Vercingetorix, an Arvernian noble whose father had been killed for seeking kingship, took the leadership.
His strategy was the significant departure from previous Gallic resistance. Rather than seeking pitched battle against legions, he adopted attrition: denying supplies, burning settlements that could feed the Romans, avoiding engagement, and striking at foraging parties and communications. Caesar describes the policy in detail, including the decision to spare the oppidum of Avaricum against Vercingetorix's advice — which Caesar then took, with the slaughter of its population.
At Gergovia the Romans were repulsed, the only clear defeat Caesar acknowledges in the campaign.
Alesia
The strategy failed when Vercingetorix allowed himself to be shut up in the hill fort of Alesia. Caesar built two concentric lines of fortification — inward to contain, outward to hold off the relief army — and won the resulting battle on ground his legions had constructed.
Vercingetorix surrendered the next day. Caesar's account of the surrender is brief and matter-of-fact; the dramatic scene of a warrior riding out to throw down his arms at Caesar's feet is Plutarch's elaboration, written much later.
He was held for six years, displayed in Caesar's triumph of 46 BCE, and executed afterwards, which was standard Roman treatment of a captured enemy leader.
Reception
From the nineteenth century Vercingetorix became a French national symbol, promoted particularly under Napoleon III, who funded the excavations at Alise-Sainte-Reine and erected a monumental statue there. That afterlife is a fact about modern France and is recorded here as reception rather than as evidence about the first century BCE.