What is meant by saying that the potential difference between two points is 1 V?

When we say that the potential difference between two points is 1 volt (1 V), it means that 1 joule of energy is required to move 1 coulomb of electric charge from one point to the other. In other words, a potential difference of 1 volt exists when 1 coulomb of charge experiences an energy change of 1 joule.

Mathematically, the potential difference (V) between two points is defined as the work done (W) in moving a positive test charge (q) between the points, divided by the magnitude of the charge:

V = W/q

In the International System of Units (SI), the unit of potential difference is the volt, and it is denoted by the symbol V. So, if the potential difference between two points is 1 V, it means that moving 1 coulomb of charge between those points requires 1 joule of energy.