It is impossible to resurrect the dead. Corpses can be transformed into obedient Inferi on a living wizard's command, though they are little more than zombies with no soul or will of their own. It is also possible via the rare Priori Incantatem effect to converse with ghost-like "shadows" of magically murdered people. The Resurrection Stone also allows one to talk to the dead, but those brought back by the Stone are not corporeal, nor do they wish to be disturbed from their peaceful rest.Death is studied in detail in a room (called the Death Chamber) of the Department of Mysteries containing an enigmatic veil (this suggests some sort of portal between the worlds of the dead and the living, but the exact significance of the veil is unclear). Sirius Black fell through this veil after he was stunned by Bellatrix Lestrange, thereby killing him.
Nearly Headless Nick in Book 5 that wizards have the choice of becoming ghosts when they pass away. The alternative is "passing on". All Hogwarts headmasters appear in a portrait when they die, allowing consultation by future generations.
In Harry Potter and the Goblet of Fire, Dumbledore says that there is no spell that can resurrect the dead, however several cases of dead people becoming half-alive are known. In the Goblet of Fire, because of a connection between Harry and Voldemort's wands, images of Voldemort's recent victims (Cedric Diggory, Frank Bryce, Bertha Jorkins, and both of Harry's parents) appear and help Harry escape. According to Harry, they seemed too solid to be ghosts.
But no one can be resurrected from death