The Evil Eye first appeared in texts from 1250BCE in Ancient Ugarit (ruins in modern-day Syria) as well as in Islamic doctrine. It was also found on drinking vessels, or eye-cups, in Greece in the 6th Century BCE and has been referenced by Plutarch, Plato, Hesiod, Pliny the Elder and others as they attempted to explain or describe its function. It has and is still widely used in many parts of the world, especially in Asia, Central and South America, parts of Europe (mostly the Mediterranean) and in some parts of North America (after being brought over by West Asian immigrants and European colonists).
It has various meanings depending on cultural practices. For some when a person wears or carries the Evil Eye, it is thought to protect them from misfortune or any negativity potentially being sent their way. There is also the belief that the Evil Eye is a look or stare that is thought to bring bad luck to the person it is intended for. You may have heard or read somewhere "May every evil eye in your life go blind", that is because it is often believed that when a person becomes more successful or steps into their power others will be envious and want to see them fail. The Evil Eye is believed to then protect you from that envious gaze and give that energy back to the sender.