It is mentioned that whole bhagvatah is exposition of first verse.

As we meditate on Supreme Truth, which is the nature of the Consciousness we realize that we are That- the Self effulgent independent Joy; the One that pervades All creation.

It further elaborated how we feel that there is illusion of Creation. We feel the this world is real but it is only a reflection. There is no creation or creator, there is only Consciousness.

The depth of this verse is beyond scope of any words!