This Chapter is called “Sight of Universal Form of God”.
After knowing the expanse of the God in chapter 10, Arjun requests the Lord to show him his magnificent Divine form.
To fulfill Arjun’s wish the God bestows Arjun with divine sight to view the humongous form of the Lord. The divine sight given to Sanjay by the Sage Vyas also allows Sanjay to see the miracle.
The God then reveals the unimaginable, huge and terrible form to Arjun. Sanjay describes to Dhrutrashtr what all he saw in that fearsome humongous form spread everywhere. Arjun too tells to Krishn what Pleasant, Fearsome and Terrible things he sees and expresses his fear.
Arjun terrified at the sight, then requests the God to come back to his original pleasant form with four arms (Lord Shreekrishn had four arms in his normal day to day appearance).
The Lord then returns to his original form to comfort Arjun.