The Elder Wand, which Harry mastered, protected him during the Battle of Hogwarts and prevented Avada Kedavra from killing him. Voldemort's use of Harry's blood inadvertently kept Lily's protective charm alive and allowed Harry to survive the Killing Curse in the forest.
It is because Voldemort killed Harry's horcrux instead of Harry himself. Voldemort didn't know that Harry was his seventh horcrux. He cast a spell on Harry, intending to kill him but instead killed the seventh horcrux, which was the last part of his soul so Voldemort dies before he can actually kill Harry.
Shortly before Voldemort attempted to kill Harry Potter, Harry had the resurrection stone and the invisibility cloak in his possession. The elder wand recognized Harry as its master even though Harry did not know this at the time.
Harry became Master of Death by owning all three Deathly Hallows and therefore cannot die. Harry sacrificed himself for his friends and therefore Voldemort's spell again rebounded. In the books, his sacrifice became like that of Lily to his friends and Voldemort's spell against them become useless.
However, becoming immortal from gathering the three is a misconception, as being a true Master of Death is realising and accepting the fact that everyone will die and there are worse things than death. Harry Potter collected the three Hallows and was willing to accept death and so became the Master of Death.
Why Harry Didn't Die in the Forbidden Forest Explained (Canon)
Why is Harry still alive after Avada Kedavra?
Harry survived Avada Kedavra multiple times due to the protection of Lily's sacrifice and the love-based magic that surrounded him. The Elder Wand, which Harry mastered, protected him during the Battle of Hogwarts and prevented Avada Kedavra from killing him.
However, the true master didn't only unite the Hallows. The true master must accept he would die, and when Harry went to his own death willingly while directly and indirectly possessing the Hallows, he became the Master of Death, because death never defeated him.
There is no Horcrux in Harry, Harry is the Horcrux. Harry survived because Voldemort took his blood in GoF. His blood contains Lily's Sacrificial Protection. As some of it lived on, in Voldemort, Harry was tethered to life.
Why didn't Harry die when Voldemort killed him as a baby?
Having willingly sacrificed her life in order to protect her infant son, Harry was placed under magical protection, so that when Voldemort cast the Killing Curse at Harry in turn, the spell backfired, leaving him unharmed (save for a lightning-shaped scar on his forehead) and Voldemort (saved by his Horcruxes) reduced ...
Despite its legendary reputation and immense ability, the Elder Wand was an unassuming object. Appearing at face value to be a wand like any other, it had a smooth, unadorned shaft and a handle formed from two conjoined spheres. The Elder Wand gave its loyalty to whoever could win it from its previous master.
How did Harry survive if he dropped the resurrection stone?
But Harry didn't die, and the reason is rather simple: when Voldemort cast the killing curse, it only killed the piece of his soul within Harry, not Harry himself. Harry then saw Dumbledore in a version of King's Cross station, something that Dumbledore said was probably happening in his head.
Notably, Voldemort appeared to be entirely unaware of this split, as he later created a seventh Horcrux in his quest to have six, and continued to target Harry Potter despite him now holding part of Voldemort's own soul.
On confirming Draco's very much alive status, she plainly lied that Harry Potter was "dead". This action of hers was both very crucial and important, not only for Harry's survival but for Voldemort's final defeat as well, thus ensuring Harry was again protected by a mother's love, although indirectly.
Harry can come back to life not only because he had the Resurrection Stone (and the other Hallows) but also because of his choices. Harry chooses to sacrifice himself, chooses to face Voldemort unarmed, and chooses to allow himself to be killed, just as he chooses to return to life.
Voldemort believed, out of his lack of understanding love, that by using Harry's blood, it would allow him to bypass Lily's protection and thereby enable him to circumvent what the boy has which robbed him of power years ago, when in fact it actually strengthened it.
Family. Snape's family background is mostly shown in flashbacks during the course of the last three novels. Snape was born to Eileen Prince, a witch, and Tobias Snape, a Muggle, making him a half-blood (hence the name, "Half-Blood Prince").
The “spell” was sacrificial protection. In order for this to happen victim must be given a choice to live and chose to die to save person or people. In this case lily was offered chance to step aside as Voldemort had promised Snape he would not kill her unless she got in way.
Hence, it could be that Voldemort's soul cannot "board a train" and leave the King's Cross purgatory as Harry could. This would mean that baby Voldemort was the combined soul fragments from the destroyed Horcruxes unable to move forward.
Snape having the same Patronus, the doe, as Lily symbolized his everlasting love and unwavering devotion towards her. He hadn't stopped loving her after their last altercation, marriage to James Potter, or death. She was his "always," his guiding light, and he protected Harry for her.
After witnessing Nagini kill Severus Snape, Harry collected a string of memories from the dying man. During a one hour ceasefire, Harry discovered that he was an unintended Horcrux from Snape's memories. In order to destroy Voldemort, he had to allow the Dark Lord to kill him.
“Is Draco alive? Is he in the castle?” The whisper was barely audible; her lips were an inch from his ear, her head bent so low that her long hair shielded his face from the onlookers.
Shortly before the Battle of Hogwarts, Harry not only successfully used the Cruciatus Curse against Amycus Carrow, he also cast the Imperius Curse against two individuals during the Gringotts heist which led to Harry, Hermione, and Ron getting in the vault.
The prophecy is mentioned throughout the series, however, it never exclusively mentions that Harry is The Chosen One and suggests Neville was another option. However, one theory explains why, in reality, this wasn't possible.
His dad gave it to him. To elaborate on Icecreamdif's answer, he inherited it as a family heirloom dating back to Hardwin Potter, who married Iolanthe Peverell, granddaughter of the Cloak's original owner Ignotus. It was passed down to the eldest male of each new generation of Potters since then.
