Short answers, pulled from the story.
The Chimera was a fire-breathing hybrid monster from Lycia, in Asia Minor, described by Homer in the Iliad as part lion at the front, part goat in the middle, and part serpent at the rear. Hesiod and Apollodorus describe it as three-headed, with each section corresponding to a different animal. It was the offspring of Typhon and Echidna, and a sibling of Cerberus and the Lernaean Hydra.
The hero Bellerophon killed the Chimera using the winged horse Pegasus. According to Apollodorus, he soared on Pegasus and shot the Chimera down from the air. Hesiod credits both Pegasus and Bellerophon together for the slaying.
Iobates, king of Lycia, sent Bellerophon to kill the Chimera because he expected the monster to kill Bellerophon instead. Apollodorus records that Iobates believed the Chimera was more than a match for many men, let alone one, and the creature had already been devastating the country and killing cattle.
The Chimera first appeared in proto-Corinthian pottery painting, providing some of the earliest identifiable mythological scenes in Greek art. The Corinthian type was fixed in the 670s BC. Two vase painters worked the motif so consistently they were given the pseudonyms the Bellerophon Painter and the Chimaera Painter.
Pliny the Elder connected the Chimera to a site in Lycia called Yanartas, meaning flaming rock in Turkish, located approximately three kilometers north of Ciralı near ancient Olympos. About two dozen vents in the ground emit burning methane of metamorphic origin, and these fires served as navigational landmarks for sailors in antiquity. The Neo-Hittite Chimera from Carchemish, dated 850-750 BC and now in the Museum of Anatolian Civilizations, is also considered a possible basis for the Greek legend.
The term chimera now refers broadly to any mythical or fictional creature assembled from parts taken from various animals. In heraldry, a chimera has the head and front legs of a lion, a goat's head on its back, the hindquarters of a dragon, and a snake-headed tail. Some western scholars of Chinese art also use the word generically for winged leonine or mixed-species quadrupeds such as the bixie, tianlu, and qilin.