Need Help Understanding a System From a Video

I had no clue how to title this but I have game similar to one of a video I just watched. Its not really a tutorial but I was wondering if anyone could point me in the right direction of how to integrate a similar attack system into my game. Specifically the smear affect working. Here is the link, and I think the part I was most confused on was 4:05 to 4:45 Making an Animation for my 3D Pixel Art Game - YouTube I’m not even sure what I should try searching up so any help in pointing me in the right direction would be greatly appreciated. Thanks in advance.

You can start by studying this free assets that will create bezier curves as in the video