Originally known as the Soul Gems or the Infinity Gems, the Infinity Stones allow anyone who holds all of them to command the universe itself. This is why they've mostly been sought out by Thanos ...

Clifford Johnson: The infinity stones are this set of artifacts that ... And then when you have them all together they make you God-like. They make you omnipotent, omnipresent, and all of these ...

This is key because the Infinity Gauntlet's purpose is to hold all six Infinity Stones, granting the wearer the ability to use the power of each stone in combination. When all six Infinity Stones ...

Thanos famously wielded (and ultimately flubbed) the Infinity Stones on multiple occasions in Marvel Comics, but now they belong to the Green Goblin.