In this shloka, Arjuna tells Bhagavān Krishna about his state of mind. He tells that his mind is confused about what is Dharma, he tells that Dharma feels like Adharma and Adharma feels like Dharma. He then surrenders to Krishna for guidance.

Bhagavān Krishna explains to Arjuna that Atma is the ultimate truth. Atma is the one which is unchangeable and exists always; All other things keep on changing and are not permanent.

Atma Swaroopa - The consciousness principle. Here Krishna explains about the Atma's nature - Nityaḥ, Satyaḥ, Sarvagataḥ, Aprameyaḥ, Akartā, Abhokthā, Nirvikaraḥ.

Krishna explains about one of the aspects of Atma which is Sarvagataḥ meaning it is present everywhere and it is not bound by space. It completely pervades the space.

Aprameyaḥ means the one who can not be understood or which is not the object of understanding. Here Krishna tells that Atma is Aprameyaḥ which means it can not be understood but it is the subject, that is all pervading.

Akartā means the one who is not the doer. Here Atma is said to be Akartā means Atma is not responsible for the tasks done by the physical body. They happen in the presence of the Atma.

Abhokthā means the one who does not enjoy the fruit of any task. Here Atma is said to be Abhokthā means Atma is not enjoyer of the fruits or outcome of any tasks done by the physical body.

Here Krishna is explaining to Arjuna about Atma. He tells Arjuna that Atma is "na hanti na hanyate" which means that the one who neither kills nor can be killed. Which means he cannot 'truly' kill his loved ones in the battle.

No Atma does not have any Pāpaṃ or Puṇyaṃ. Bhagavān Krishna has explained that as Atma is neither the doer nor the enjoyer and is Nityaḥ, it does not have a birth nor death, thus it does not have any Pāpaṃ or Puṇyaṃ.

The more pervading something is, the more it loses its shape. When something is all pervading, there would be no form at all.