Without expo, if you move the stick 1/4, the control surface (CS) moves 1/4

Move the stick 1/2, the CS moves 1/2 ETC

But with expo, you can bend that straight line to a curve.

The actual amount of movement will vary depending on the amount of expo you dial in, but to give you an idea, it can be set so that:

When you move the stick 1/4, the CS moves 1/16

Move the stick 1/2 and the CS moves 3/16

Move the stick 3/4 and the CS moves 1/2

Move the stick all the way and the CS moves all the way