Hear from Me in essence: What that Field (kshetra) is, what are its characteristics and various modifications, wherefrom and how it has originated; and also what He (the Kshetrajña) is and what are His powers.
Although there are innumerable fields of activity, the Knower (Kshetrajna) is only One. How this is so will be explained subsequently.
The world or creation being vast and extensive, activities in it are obviously infinite. Every object is a kshetra, hosting its activities. But the Kshetrajna is the same in all. In other words, the ken of matter and energy is quite extensive, necessitating numerous kshetras, activity centres. But the sentience present in them is singular, unfragmented. The One co-existing with endless many.
This is no contradiction; instead it is a harmony, amazing in every way, warranting deep research. Krishna adds that true knowledge is that wherein one knows well both the kshetra and Kshetrajna. In fact, this ‘one in many’ is the sole message of the entire dialogue.