How does superstring theory include a possible quantum particle of gravity called the graviton?

In superstring theory, the graviton—the hypothesized quantum carrier of the gravitational force—is included naturally as a consequence of the theory's mathematical framework.12

Unlike conventional point-particle models that struggle to incorporate gravity into a quantum field theory, superstring theory models elementary particles as tiny, one-dimensional vibrating strings. In this framework, the mass and charge of a particle are determined by the specific vibrational pattern of the string.324

Physicists have found that among the various vibrational modes predicted by the theory, there is a massless particle with a spin of 2 units. This specific vibrational state corresponds to the properties required for the graviton. Because the theory requires this particle to maintain mathematical consistency, superstring theory automatically incorporates a quantum description of gravity, effectively merging quantum mechanics with general relativity.213