Imagine you tie a golf ball to a fan and lie beneath it and mapped its position. The golf ball would make a circle, and we could graph its movement using the x-y coordinates.

Now imagine you’re looking at the golf ball from the side. It’s still making the same movements, but it’s difficult to graph it’s movement because it looks like it’s only moving along the x axis.

In this example, imaginary numbers are the missing coordinate plane. They help us graph the behavior even though part of the movement doesn’t necessarily make sense/isn’t visible from our perspective.