Infinity Stones

Infinity Stones are six immensely powerful objects that hold predominance over the universe. Before the universe was created, the Infinity Stones existed as a singular force. It is unclear whether the universe was created by the splitting of this singularity or if the creation of the universe generated the force which split the singularity into six discrete stones. Each of the stones possesses unique capabilities that have been enhanced and altered by various alien civilizations through the millennia. Only beings of immense power can wield the stones, such as when the Celestials used the Orb to pass judgement on entire planets. Lesser beings are usually unable to grasp the full power of the stones and are destroyed by them when direct contact is made, such as the illness of Jane Foster when exposed to the Aether, the disappearance of the Red Skull by the Tesseract, and the incineration of Carina by the Orb. Only once in recorded history has the power of all six stones been harnessed. This was achieved by six cosmic beings, each with one stone, linking themselves together. The effects were short-lived as the energy of the stones disintegrated all six beings after a few short moments. Despite being referred to as "stones," the Infinity Stones appear in different shapes and states.

Powers and Abilities
Each of the Infinity Stones have the ability to be used individually by powerful beings or collections of lesser beings who focus their intent. The power of all six stones can be harnessed collectively, but none who have attempted this have survived.

Trivia

 * In the comics, the six Infinity Stones, known as the Infinity Gems, consist of Mind, Soul, Power, Space, Time and Reality. Kevin Feige confirmed the Tesseract represents the Space Stone, and the Orb has been revealed to be the Power Stone, but it has not been revealed what the other Stones represent.
 * Due to the appearence of Thanos, fans have speculated that the Blue Crystal within the Chitauri Scepter is the Mind Stone from the Infinity Gauntlet.