Short answers, pulled from the story.
Hades is the god of the dead and King of the underworld in ancient Greek religion and mythology. He was the eldest son of the Titans Cronus and Rhea, and the brother of Zeus and Poseidon. After the gods defeated the Titans in the Titanomachy, the three brothers drew lots to divide the cosmos, and Hades received the underworld.
Fear of attracting his attention led Greeks to avoid pronouncing his name, particularly from around the 5th century BC onward. They substituted euphemisms such as Plouton (the rich one), Polydegmon (host of many), and Clymenus (infamous). Sophocles explained the Plouton title by saying the gloomy Hades enriches himself with sighs and tears.
Hades abducted Persephone, the daughter of Zeus and Demeter, while she was picking flowers in the fields of Nysa. Demeter cursed the land with famine until her daughter was returned. Zeus sent Hermes to negotiate Persephone's release, but Hades secretly gave her a pomegranate seed to eat before she left, binding her to the underworld. The compromise reached was that Persephone spends one third of each year below, during which winter falls on the earth.
Orpheus descended into the underworld to find his wife Eurydice, who had died from a snake bite. His music was so beautiful that it moved Hades and Persephone, and Hades allowed him to lead Eurydice back to the living world on the condition that he not look back at her. Orpheus looked back before they reached the surface, and Eurydice was lost.
Sisyphus, a mortal king from Corinth, was punished for revealing to the river god Asopus the whereabouts of Zeus's abducted daughter Aegina, and for repeatedly trying to cheat death. His eternal punishment in Tartarus was to roll a boulder up a hill, only for it to roll back down every time he neared the top.
Hades was depicted infrequently in ancient Greek art because the Greeks feared him. His earliest images appear in Archaic pottery, where he is shown with a dark beard seated on an ebony throne. His attributes include scepters, cornucopias, roosters, and the Key of Hades. As Pluto, he was portrayed more favorably, holding a cornucopia and connected with fertility.