Sacrificial protection

The Sacrifice charm is one of the most powerful magic phenomenon in the HP universe. When a person sacrifice him-herself for another person they are willing to die for a powerful protection is created.

Effects
It is know to protect form the Killing Curse and it is unclear if it protects from other spells.

Known cases
Harry Potter is so far the only person to have been protected by this spell from Lord Voldemort when Lily Potter sacrifices herself for him, possibly the allies off Harry during the Battle of Hogwarts after he had sacrificed himself for them but in the case of the Horcruxs he survived. But this is not confirmed

Department of Mysteries, the Love chamber
The Love chamber is in the Department of Mysteries and is the place where the Ministry research about how love protects from the Killing Curse. for more information see Department of Mysteries.