Short answers, pulled from the story.
The first battle occurred on the 3rd of October 42 BC and the second battle took place on the 23rd of October 42 BC. These two engagements defined the conflict between the Liberators and the Second Triumvirate.
Brutus and Cassius led the Republican forces known as the Liberators while Mark Antony, Octavian, and Lepidus formed the Second Triumvirate. Gnaeus Domitius Ahenobarbus commanded the Republican fleet that attempted to block supply lines from Italy.
The fighting occurred near the city of Philippi in Thrace along the Via Egnatia. The battlefield stretched across a wide plain west of the city with marshes to the south and hills blocking the northern side.
Cassius ordered his freedman Pindarus to kill him because thick dust clouds prevented him from seeing Brutus's victory on the other flank. He mistakenly believed his entire army had been crushed by the triumvirs' forces.
Cassius lost 8,000 men while Octavian suffered about 16,000 casualties during the first day of fighting. Roughly 14,000 men from the Liberators' army were eventually enrolled into the triumvir forces after their defeat.