* Lily's Sacrifice: Lily Potter, Harry's mother, sacrificed her life to save her son. This act of selfless love created a powerful magical shield around Harry.
* Love's Power: Love, according to the wizarding world, is a potent magic. It was powerful enough to deflect the Killing Curse, which is a spell designed to sever the soul and bring instant death.
* Lily's Love Linked to Harry: Lily's love for Harry was so strong that it bound her to him, even after her death. This bond was a key factor in the spell's failure.
* Voldemort's Weakness: Voldemort, despite being a powerful wizard, had never understood or experienced true love. This fundamental lack of understanding left him vulnerable to its power.
In short: Lily's sacrifice, fueled by her immense love for her son, created a protective barrier that the Killing Curse could not penetrate. It was this act of love, not a flaw in the spell itself, that saved Harry's life.