We only know one druid by name and that is Diviciacus, a druid from the Aedui tribe in France, known then as Gaul. He met Cicero, a very famous Roman politician and speech maker, and fought with Julius Caesar.
Druids were the lawyers, natural scientists, astronomers, mathematicians and religious leaders of the Celts. According to Julius Caesar, they did not believe in writing things down, but memorized all their knowledge, which could take up to twenty years. There were special schools for boys and girls to study under the druids, and one of these was in the tribal lands of the Aedui, in Augustodunum, now called Autun.
The Romans told many stories of druids telling the future and performing human sacrifices. Some sacrifices have been found, such as the preserved bodies of men and women found in bogs in Britain, Ireland and Scandinavia. Some of these are believed to be kings, who were killed if harvests were failing or other disasters fell upon their people. Their death made way for a newer king, hopefully more favored by the gods. Others, according to Julius Caesar, were criminals. The Romans tended to make the druids sound barbaric, but the Romans themselves were equally scary. They were merciless in war, loved gladiator fights and mistreated slaves.
The Aedui tribe were friends to the Romans so when they were being attacked by neighboring tribes, Diviciacus, as a druid and diplomat for his people, travelled all the way to Rome and spoke to the Roman Senate to ask for help. In the Battle of Magetobriga, he told the Senate, many of the Aedui were killed by the Sequani and Arverni tribes, who were helped by the German Suebi tribe lead by King Ariovistus, who wanted more land. This worried the Romans and Julius Caesar is believed to have used this plea for military aide as an excuse to return to Gaul and defeat Ariovistus and the other Celts once and for all.
There was one very tricky problem. Diviciacus had a brother, Dumnorix who really hated the Romans. When Dumnorix was captured by Caesar, Diviciacus had to plead for his life. Whether Diviciacus was a good friend of Caesar's or just really persuasive, we will never know for sure, but Caesar agreed to let his brother live.