object declaring keyword in javascript

Question

What is the different between new keyword and no keyword in declaring object.

var person = function(){
    return {
        name: '',
        age: 0
    }
}

var mgmg = person();
var koko = new person();

mgmg.name="mg mg";
koko.name="ko ko";

alert(mgmg.name);
alert(koko.name);