Ch 2:Verse 16

2:16
nāsato vidyate bhāvo nābhāvo vidyate sataḥ
ubhayor api drshtonta tvanayostattva-darśibhiḥ

There is no existence for the unreal.
There is no non-existence for the real(atma).
The difference between the two is known to those who see the truth.

You are not the body.You are not the mind.You are something beyond these.You are the atma.

The difference between the atma and anatma(objects of the material world,which include the human body) can be illustrated by a simple example.Take gold,a block of gold.Of what use is it?(Other than being capable of breaking someone's skull if thrown).Take a golden bangle,a necklace,a gold ring.What do you see?A thing of utility.
But you must realize that the value that the bangle or the necklace carries is not its own.The bangle's value is of the gold with which it is made.The gold is the essence of the bangle.The piece of jewellery,though of great utility,holds no value of its own.Try melting it,and you'll know.On the contrary,gold,though of no practical utility by itself,is the essence of every form of jewellery.Likewise,the atma,though unseen,is the essence of different forms of objects(read living beings).
All living beings are in one way or another,a form of the atma.The atma is permanent,imperishable,existed before,during,and will continue to BE after the destruction of the human body.