ok as promised...
A- is for aperture priority, which means you get to control the aperture.
Aperture is very hard to explain, and took me a while to really get...
I am going to give you the explanation in points in hopes it will be easier to understand:
-if reading your manual and it talks about F stop, that is the same as aperture
-the F stop is the number that determines how wide the shutter is open.
-Aperture/F stop is represented by a number, the smaller the number the wider the opening, the larger the number the smaller the opening.
-smaller aperture = shorter field of distance, field of distance is the amount of what is in focus in your photo.....
ok, why might you want to know this???
Do you like those pictures where the background is blurred and the foreground isn't?
Knowing how aperture works is how that happens, OR when the foreground is blurred and the background isn't... remember this, the lower the number the more is out of focus!!!
HOWEVER... this isn't the only thing you need to know when trying to achieve that look. you have to be mindful of the distance between you and your subject(what you want in focus) as well as the distance between your subject and the background you hope to blur... you want your subject closer to you, and the background further back from your subject.
I hope that made an ounce I know it confused me at first!!