In this chapter we made image files into both "brushes" and "textures" folders... but what is the difference? What should go where?
This will be cover in the next chapter. Textures are the images. Texture Brushes use the image to give different brush effects. It has been awhile since I watched this, but if I remember correctly the Brush is all the settings. The texture is the image that is added to the brush's material. I don't remember if the thumbnail is part of this chapter or next, but that is another image and I believe folder.
Thankyou Dwayne! Yes, the "brush" folder will house the icon that Blender searches for when displaying the brush in the interface, and textures will house the actual texture. Keep in mind, this is for any version before 4.3, before Grease Pencil got its recent glow-up. It's a little different now. I will be happy to talk you through the current set up in your submission.