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

When 1 Joule of work is done to move a charge of 1 coulomb from one point to another, then the potential difference between the two points is said to be 1 V.

$\therefore 1 \text{ Volt} = \dfrac{1 \text{ Joule}}{1 \text{ Coulomb}}$