The discussion centers on the concept of whether pure energy can possess mass and form a gravitational entity. It clarifies that energy is not a substance, and the term "pure energy" is largely a science fiction construct. Photons, while having momentum, do not have rest mass, but they are considered a fundamental form of energy. Energy is defined as a property of objects or systems, similar to mass and momentum, and cannot exist independently. The conversation emphasizes that there is no such thing as "pure energy" without association to an object or system.