What are the Deathly Hallows?

The Three Deathly Hallows are:
The Elder Wand - Antioch Peverell
Invisibility Cloak - Ignotus Peverell
Resurrection Stone - Cadmus Peverell

The Three Peverell Brothers are also known as in the book The Tale of Beedle The Bard.
Ignotus is Harry Potter's ancestor therefore making him rightful owner of the The Invisibility Cloak.

The Elder Wand is unbeatable, and passes its allegiance on to the person who has won or killed its previous master.

The Resurrection Stone has the ability to bring back the dead, though the people brought back are not happy because they are not in the right world. The holder of the stone must maintain hold of the stone for the dead to remain in the living world, and they are only perceivable to the owner.

The Invisibility Cloak makes you invisible. The cloak is immune to all forms of charms and jinxes. It cannot be destroyed or detected by magic unless with the use of devices capable of seeing through physical matter (Mad-Eye's magical eye).

All together they make the Deathly Hallows and the owner of all three would be known as the Master of Death (in legend). The sign for the Deathly Hallows is a Triangle with a circle in it then a line going straight down the middle. The symbol is also the symbol of Grindelwald, whose ambition was to find all three Deathly Hallows, which was Dumbledore's early ambition as well.

The stone is given to Harry by Dumbledore in his Will through the use of the first Snitch Harry caught as to avoid detection from the Ministry. The Elder Wand, also known as the Deathstick, the Wand of Destiny and other names, becomes under the allegiance of Harry Potter as he forcefully removes Draco Malfoy's wand out of his hand. Malfoy was its previous master as he disarmed Dumbledore moments before his death. After Harry defeats Voldemort, and he returns it to Dumbledore's tomb, symbolising that he is entrusting it to him and once he dies, the wand's allegience will return to Dumbledore and it's power will drain away.