According to legend, Cheiron was sired by the Titan Kronos and the nymph Philyra. In the midst of copulating with Philyra, Kronos' wife Rhea suddenly appeared and to escape her notice, he transformed himself into a horse thus resulting in the half-human and half-equine Cheiron who was the first Centaur. Due to his lineage, Cheiron was immortal and would be taught by the Olympian Gods Apollo and Artemis.
Due to their teachings, Cheiron became renowned as a scholar and skilled in the arts of astronomy, archery, hunting, swordsmanship, healing, and a great oracle as well. He married a nymph Chariclo who bore him several daughters Hippe, Endeis, and Ocyrhoe and a son Carystus. He became revered as a superlative teacher and as a result, he personally instructed and taught a number of individuals over the course of his life.
His many students included some of the greatest Greek heroes such as Jason who would become known as the leader of the Argonauts; the legendary hunter Actaeon; Theseus who killed the Minotaur; a maiden known as Caeneus who was raped and begged to never have such a fate happen to her again was transformed by the Gods into a male warrior who possessed a supernatural invulnerability to any weapon; Peleus who was the father of the invulnerable Achilles who was another of Cheiron's students; the Trojan hero Aeneas; Ajax the Great; Perseus, the famous slayer of Medusa; and the legendary Heracles.
However not all of his students would be great warriors. He also instructed Asclepius in the art of healing and would became such a famous healer that he possessed the power to resurrect even the dead and it is said that out of fear, Hades himself had Zeus slay him in order to prevent the healer from cheating him of his rightful tribute by emptying the populace of the Underworld; Aristaeus who developed the art of nets and traps for hunting and the art of dairy skills and cheese making, bee keeping, and how to raise olives; and even Dionysus prior to his assumption of godhood.
Cheiron and his daughters also was responsible for raising the Centaur tribe when they were spawned by Ixion and Nephele. Although many of them were wild overindulgent drinkers and delinquents and were not directly related to him; all of them deeply honored and revered Cheiron as the first of their "kind" and the greatest of them all.
However his immortality did not prevent him from being poisoned by the blood of the Hydra when he was accidentally wounded by Heracles. In great and constant pain and unable to die, Cheiron willingly relinquished his immortality in exchange for freeing Prometheus.
In tribute of his life and noble sacrifice, Zeus would choose to raise Cheiron as one of the constellations Centaurus; immortalizing him and his works.
Cheiron's name was apparently derived from the Greek word 'kheir' which means "hand" or more appropriately "skilled with hands". The word would also be associated with 'kheirourgos' or in it's more modern form, 'surgeon' which probably owes itself to Cheiron's legendary healing skills.