Short answers, pulled from the story.
Sulla's civil war was an armed conflict in the Roman Republic fought between the general Sulla and the Marian faction, the followers of Gaius Marius and Lucius Cornelius Cinna, in 83 to 82 BC. It ended with a decisive battle outside Rome, after which Sulla declared himself dictator.
In the spring of 83 BC, Sulla landed his army in two divisions in southern Italy: one at Brundisium and one at Tarentum. He offered sacrifices at Tarentum before advancing inland.
At Sacriportus, near Signia, Gaius Marius the Younger attacked Sulla's camp while it was still being dug. Sulla's veterans repelled the assault; five cohorts of infantry and two of cavalry deserted to Sulla mid-battle, triggering a full rout. Marius the Younger lost 28,000 men and retreated to Praeneste with only 7,000 survivors.
An estimated 50,000 men lost their lives at the Battle of the Colline Gate, the final decisive engagement of Sulla's civil war fought just outside the walls of Rome.
Sulla's proscriptions were a program of state-sanctioned executions paired with property confiscation targeting those he considered enemies of the Republic. He ordered the deaths of some 1,500 nobles including senators and equites, though the actual death toll is estimated at as many as 9,000. The confiscated property was auctioned, generating more revenue than the cost of the rewards paid to those who carried out the killings.
When relatives of Caesar persuaded Sulla to spare the young man, Sulla reportedly warned them he would become dangerous, saying: "In this Caesar there are many Mariuses." This remark was recorded by the historian Suetonius, and Sulla also noted in his own memoirs that he regretted the decision to spare Caesar.