When you make a new layer it shows up in your Layers Palette, called Layer 1. You can rename it, if you like, but what we're really interested in is the little eyeball button to the left of it, which the arrow's pointing at.
This eyeball turns the layer on and off. If you can see the eyeball, then you can see the layer. If you can't see the eyeball, the layer is turned off, or is invisible.
More on this later.
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