Understanding 'Prototype' concept in Js

The prototype property of a function contains an object. It is only useful when you use this function as a constructor.
All objects created with this function keep a reference to the prototype property and can use its properties as their own

var some_obj = {
name: 'Arif',
say: function(){
return 'I am ' + this.name;
}
}

function F(){}
F.prototype = some_obj;

>>> var obj = new F();
>>> obj.name
"Arif"
>>> obj.say()
"I am Arif"