Short answers, pulled from the story.
Pyrrhus of Epirus (319/318-272 BC) was a Greek king of the Molossians and king of Epirus who became one of the strongest opponents of early Rome. He is famous for giving the world the phrase "Pyrrhic victory," derived from his remark after the Battle of Asculum in 279 BC that one more such costly victory would utterly ruin him. Hannibal ranked him among the greatest commanders who ever lived.
A Pyrrhic victory is a victory won at such heavy cost that it is effectively worthless. The term comes from Pyrrhus of Epirus, who after defeating the Romans at Asculum in 279 BC reportedly said: "If we are victorious in one more battle with the Romans, we shall be utterly ruined." The battle cost him 3,500 men, including many officers.
Pyrrhus died in 272 BC during street fighting in Argos. While he was engaged with an Argive soldier, the soldier's elderly mother threw a roof tile from above that struck Pyrrhus and broke part of his spine, paralysing him. A Macedonian soldier named Zopyrus then beheaded him. The story was later recorded by Plutarch in his Life of Pyrrhus.
Pyrrhus fought Rome at the request of the Greek city of Tarentum, which faced Roman conquest after attacking Roman warships and garrisons in 282 BC. He won costly battles at Heraclea in 280 BC and Asculum in 279 BC, but suffered unsustainable losses each time. After a failed campaign in Sicily and defeat at Beneventum in 275 BC, he withdrew to Epirus, losing all his gains in Italy.
Pyrrhus arrived in Sicily in 278 BC, quickly lifted the Carthaginian Siege of Syracuse, was proclaimed king of Sicily, and in 277 BC captured Eryx, the strongest Carthaginian fortress on the island. His attempt to besiege Lilybaeum failed after two months, and his imposition of military rule alienated the Sicilian Greeks. He left in 278/277 BC, and his fleet was largely destroyed by Carthaginians at the Strait of Messina, with 98 of 110 warships sunk or disabled.
Pyrrhus first became king of Epirus in 307 BC at age eleven through the intervention of Glaucias of the Taulantians, but was deposed while still a teenager when the Molossians rebelled during his absence. He regained the throne in 297 BC with the financial and military support of Ptolemy I Soter. He also ruled Macedonia jointly with Lysimachus from 288 BC before being driven out in 284 BC by Lysimachus, and again seized most of Macedonia in 274 BC.