In the law of universal gravitation eequation what does the d stand for?

In the law of universal gravitation equation, ( F = \frac{G \cdot m_1 \cdot m_2}{d^2} ), the variable ( d ) represents the distance between the centers of mass of the two objects involved. This distance is crucial because the gravitational force decreases with the square of the distance, meaning that as the distance increases, the gravitational attraction between the two masses diminishes significantly.