You've got it Michele! wohooo!!
Your lens 18-55mm 1:3.5-5.6 means that when you are at a focal length of 18mm you can shoot at f/3.5 (your widest aperture) but when you are zoomed out to 55mm your widest aperture is f/5.6
In A mode you can't control your shutter speed, the camera chooses it. A means aperture priority so the aperture "takes priority" and is then all you can control.
If you want to have complete control then switch on over to M (manual) and you get to control everything!
Hope this helps!! Love your questions, keep them coming!
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