The top shows Newton’s formula for calculating gravitational force between two bodies. The bottom shows Coulomb’s law for calculating the force between 2 electrically charged particles. The joke is that the Coulomb just copied the formulas from Newton’s that was published nearly a century earlier.
With how gravity isn't a force in general relativity meaning Newton's formula isn't technically correct in a general sense makes it funny Coulomb's "copied" formula turned out to be the correct one.