The Electric Potential
Consider an electron $\sf{e}^{-}$ located at some position noted by $\overline{r}$. The frame-of-reference for this space is provided by + a proton. The electon's position and tripartite dimensionality is presumably established by a history interactions with + and $\, \gamma _{\tiny{\bigcirc}}$ a photon that is part of the proton's electromagnetic field.
Bringing an electron into the description changes the configuration of quarks in the frame, and this requires that some work be done. As discussed earlier we note the work needed to establish the proton and photon by $W$. And $W^{\prime} \left( \overline{r} \right)$ notes the work required to assemble + and $\, \gamma _{\tiny{\bigcirc}}$ with $\sf{e}^{-}$ at $\overline{r}$. Then these quantities determine $\mathcal{V}$ the electric potential as
\begin{align} \mathcal{V} \left( \overline{r} \right) \equiv \frac{W^{\prime} - W }{q} \end{align}
where $q$ is the charge of the electron. The conventional unit used when measuring an electric potential is called the Volt abbreviated by (V). And any difference in electric potential between two positions is known as a voltage.