A layer helps you organize objects so you can work with your document in a way that makes sense to you. You can also hide or lock an entire layer.
In this example, “Canvas 1” contains four separate layers, and three of them are Shared: Layer 1 contains the web browser window to frame everything, Layer 3 and Layer 4 are shared resources, and Layer 2 is unique to each canvas. Double-click a layer to give it a unique name.
You’ll also find Artboard Layers here (used for defining specific areas on the canvas). Learn more about them here.