Yeah basically think about it as what comes before and what comes after. So you have something over here and then you have something else. As Martin’s pictures show, you have 3 incoming edges and then they turn into 1 outgoing edge. Then in the other one you have 4 edges and then you only have 2 edges. So it’s 3 to 1 and 4 to 2.
It’s like alchemy. You have 4 of a certain stuff and you’re like man 4 is too much, I can’t deal with 4, let me do the alchemy magic and bam, now I have 2, much easier to deal with 2. When you model things in 3D, too much geometry can be hard to control, so it’s a way to simplify the mesh to gain more control.
