__proto__ is a property for object.prototype which is accessor of prototype that expose the prototype object which can be reused for other objects or other prototypes!
For example :
const obj = {
method: function() {
console.log("method in obj")
}
}
const obj2 = {}
obj2.__proto__ = obj // here we can see that __proto__ makes obj2 fulfilled with obj!
obj2.method()
JavaScript
For reference :
