electric potential
Electric potential is the electric potential energy per unit charge at a point, a way of describing the electrical push available at a place without yet saying what charge you will put there. It is the quantity your multimeter calls voltage. If the field is like the steepness of a hill, the potential is like the height of the hill: charges roll from high potential to low, the way balls roll downhill.
The electric potential V at a point is defined as V = U / q, the potential energy a charge q would have there, divided by q. Its SI unit is the volt (V), where 1 volt = 1 joule per coulomb. For a single point charge Q, the potential at distance r is V = k Q / r. The energy of a charge q placed at potential V is U = q V, and the work to move a charge between two points is q times the potential difference, W = q (V_A - V_B). The field points from high to low potential, downhill on the potential landscape.
Potential is enormously convenient because it is a single number at each point (a scalar), not a direction-bearing vector like the field, so potentials from many charges simply add up arithmetically. Batteries are rated by the potential difference they maintain (a 9-volt battery), and every circuit is analysed by tracking potential from point to point. The difference in potential between two points is called voltage.
At 1 cm (0.01 m) from a 1-nanocoulomb charge, V = (8.99 x 10^9)(10^-9) / 0.01 = about 900 V; a charge placed there has energy U = q V waiting to be released.
Potential is energy per coulomb, so it adds up as plain numbers, not vectors.
Only potential differences matter; the point you call zero volts (often the ground or infinity) is your choice. 'The voltage at a point' always secretly means relative to some agreed reference.