The current layer
When you draw on the Canvas, modifications are only applied to the current layer. This layer will bear a lighter gray than the others in the Layer Stack:

To change the current layer you can:
- Use the [↑] and [↓] arrow keys on your keyboard.
- Click on the layer of your choice in the Layer Stack.
tip
Another tip consists in using the [","] shortcut to select a layer from the Canvas.
Pressing this key will turn your cursor into an arrow bearing a question mark allowing you to select a pixel with color information on the Canvas:
- If there only one pixel at those coordinates, the layer it belongs to will turn into the current layer.
- If there are several pixels at those coordinates, you will be able to choose one layer from the ones they belong to thanks to a pop up window: