<html>
<script language="JavaScript">
var object1 = {value: 10};
var object2 = object1;
var object3 = {value: 10};
alert(object1 == object2);
alert(object1 == object3);
object1.value = 15;
alert(object2.value);
alert(object3.value);
</script>
</html>
object1 and object2 are two variables grasping the same value. There is only one actual object, which is why changing object1 also changes the value of object2. The variable object3 points to another object, which initially contains the same properties as object1, but lives a separate life.
JavaScript's == operator, when comparing objects, will only return true if both values given to it are the precise same value. Comparing different objects with identical contents will give false.