There is some confusion as to the heritage of the Fates but there is no confusion as to their identities and their divine mission on the earth. Their names are: Klotho (Clotho), Lachesis and Atropos. Klotho spins the thread of life, Lachesis determines the length of the thread and Atropos cuts the thread when the proper time has come for death. Atropos is the smallest of the three but she is the eldest and superior to her sisters. Atropos is called "She who cannot be turned."
The three sisters are commonly called the Fates but Fates and Destinies seem to be interchangeable with most translators.
In the poem Theogony by Hesiod, the distinction is clearly made between Black Fate (Kera), the Destinies (Moerae) and the Fates (Keras). We are told that the Fates are the children of Nyx (Night) ... their names are: Klotho, Lachesis and Atropos (line 217). However, we are also told that the Destinies are the daughters of Themis (goddess of Necessity) and Zeus ... their names are: Klotho, Lachesis and Atropos (line 904). Which explanation are we to believe? We are left with a mystery which may never be solved until some heretofore unknown ancient documents are unearthed.
The distinction between Fate and Destiny might seem to be inconsequential but, although they are closely related, there are important differences and thus the differences apply to the goddesses of Fate (Keras) and the goddesses of Destiny (Moerae). Fate is a concept which implies something which will happen but is still subject to change. Destiny is fixed and unalterable ... no one can change Destiny. The mission of the Fates seems more akin to the fulfillment of Destiny than any sort of alterable fate.
The intervention of the Fates in human affairs did not begin until after the creation of the first woman. Zeus commanded the Immortals to create a woman as punishment for the crimes of the Rebel God, Prometheus. On two occasions, Prometheus insulted Zeus: once by not offering the prime meat of a sacrificial animal and another time by stealing fire and giving it to the men on the earth. Zeus had Prometheus chained to a mountain for his crimes but he also tricked Prometheus's brother Epimetheus into accepting a divinely created woman. The woman's name was Pandora. Her name means, All Endowed, i.e. each of the Immortals contributed to Pandora's inception. Pandora was intended to be a curse on the men of the earth and she fulfilled her destiny superbly.
Before Pandora, men lived free of ills ... men were not subject to hard toil and were free of sickness. After the creation of Pandora, the Fates inflicted all manner of evil and hardship on the men of the earth. From that time until now, the portion of good or bad which each man will experience in his life is determined by the Fates at his birth. Once your thread of life is spun and measured, there is no escaping your final Fate ... when Atropos cuts your thread of life, there is no reconciliation.
The Fates are ruthless and without pity or remorse. When Hephaistos (Hephaestus) made a shield for Herakles (Heracles), he included images of the Fates which were ugly and terrifying. The three sisters gnashed their fangs as they stalked soldiers on the battlefield and waited to drink their blood. The Fates will never cease from their punishment of wrongdoers ... they punish the Immortals as well as mortal men with severe penalties for their transgressions.