What layers are actually for
Most explanations describe layers as sheets of transparent plastic, which is accurate and useless. The point of layers is that you can change your mind later.
Every tutorial explains layers the same way: imagine sheets of clear acetate stacked on top of each other. This is true, and it tells you nothing about why you would bother.
The actual reason is simpler. Layers exist so that a decision you made twenty minutes ago is still a decision, not a fact.
The problem they solve
Open a photograph in a basic editor. Paint over a blemish. Add text. Crop. Save.
Now the client wants the text moved, the crop undone, and the blemish left in. Every one of those is impossible, because each edit destroyed the pixels underneath it. The only route back is undo, which means undoing everything after it too, and only if you have not closed the file.
With layers, the photograph is one layer, the retouching is another, the text is a third. Moving the text is dragging it. Removing the retouching is deleting a layer. The photograph underneath was never touched.
That is the whole idea. Everything else is detail.
The kinds you will meet
Pixel layers hold actual painted or photographic content. Your image, your brush strokes.
Text layers stay editable as text. This matters more than it sounds: text rasterised into pixels cannot be corrected when you notice the typo, and you will notice the typo.
Shape layers hold geometry — rectangles, circles, lines — that stays crisp at any size and can be recoloured without repainting.
Adjustment layers are the interesting ones. Instead of changing the pixels below them, they hold an instruction: "make everything under this 20% brighter". The pixels stay untouched; the instruction is applied when the image is drawn. Turn it off and the brightness change is gone, completely, at any point in the future.
Masks control where a layer is visible, using black and white rather than deletion. Paint black on a mask and that part of the layer hides. Paint white and it comes back. Nothing is erased, so nothing is lost.
Groups hold other layers so a composition with thirty elements has six things in it.
Masks are the part worth learning
If you take one thing from this article, take masks.
The instinct when you want to remove part of a layer is to erase it. That works, and it is permanent. The alternative is to add a mask and paint black over the area you want hidden — visually identical, completely reversible, and adjustable with a soft brush for edges that need to blend.
The rule people remember it by: black conceals, white reveals. Grey partially reveals, which is how you get a gradual fade.
This is how a background gets removed by hand: mask the subject, refine the edge, and if you cut too far you paint it back. No automatic tool needed and no destroyed pixels.
Order and its consequences
Layers are drawn bottom to top. The thing at the top of the stack covers what is below it. If your text has disappeared, it is almost certainly under something rather than gone.
This trips people up constantly, and the debugging step is always the same: hide layers from the top down until the missing thing appears.
Where people go wrong
Working on the background layer directly. Duplicate it first. Then the original is intact and the duplicate takes the damage.
Flattening too early. "Flatten" merges everything into one layer. It makes the file smaller and throws away every decision. Do it on export, never on the working file.
Not naming anything. Layer 14 copy 3 means nothing tomorrow. Twenty seconds of naming saves ten minutes of clicking through eyeballs to find the right one.
Saving to JPEG and expecting layers to survive. They do not. JPEG and PNG are flat. Layers live in the editor's own project format — keep that file, export the flat one.
Doing this in Miyu Paint
Miyu Paint's free tools cover opening, cropping, resizing and drawing, with PNG and JPEG export up to 2048 pixels on the longest edge and no watermark. That is enough for a quick edit and does not involve layers at all.
Full access adds the layer system this article is about: pixel, text, shape, group, mask and adjustment layers, so a composition stays flexible as it grows. It also adds saving editable .mpaint project files — which is the part that makes the whole thing worthwhile, because layers you cannot save are layers you lose when you close the window.
Alongside that: brushes, pencils, erasers, fills and selections, plus adjustments, effects, advanced formats and printing. Undo, redo and local recovery are there for the times the layer discipline slips.
The trial is fourteen days and you start it yourself. It does not begin when you first open the app and it does not renew into a charge. Editing happens on your Mac — no account, no advertising, no analytics.