Signed distance functions are an incredibly powerful technique to define 2D or 3D shapes using mathematical formulas. If you have ever checked if a point is inside a circle or inside a rectangle, you have already unwittingly used a signed distance function. There are many more formulas that define many more shapes, as well as tricks to transform and combine them.
If you are using shaders you will find SDFs come very naturally, but if you don’t, they’re still very useful.
It’s mainly a matter of recognizing that you are using or could be using an SDF, because they got superpowers.
I made a video!