Coulomb's Law

To quantify electric interactions we use an equation known as Coulomb's Law $$\vec{F}_{elec\space on \space 2 \space by \space 1} = \frac{1}{4\pi\epsilon_0}\frac{q_1q_2}{|\vec{r}|^2}\hat{r}$$
$\vec{r} = \vec{r}_2 - \vec{r}_1$ is the position of 2 relative to 1.
$\frac{1}{4\pi\epsilon_0}$ is a universal constant, equivalent to $9\times10^9 \frac{Nm^2}{C^2}$
The charges $q_1$ and $q_2$ are measured in units of Coulombs, abbreviated $C$.

Like gravity, it is proportional to the inverse square of the distance between the center of its objects.  The universal constant is much larger than that of the gravitational constant, meaning that the electric interaction is much stronger than gravitational interaction.