The Layers explained

The PDF is composed of multiple images. That’s correct. Using a photo editor or PDF viewer of your choice, you can extract this image data, view it, hide it, etc. But these layers, as they’re being called, aren’t layers in the traditional photo-editing sense of the word. They are, quite literally, pieces of image data that have been positioned in a PDF container. They appear as text but also contain glyphs, dots, lines, boxes, squiggles, and random garbage. They’re not combined or merged in any way. Quite simply, they look like they were created programmatically, not by a human.