You can try this. Do it outdoor where there are plenty of light. Maybe take a photo of a leaf.
1. Take the photo in AUTO mode.
2. After that, note down the Aperture, Shutter Speed and ISO settings.
3. Go to manual mode.
4. Set the Aperture, Shutter Speed and ISO settings according to step number 2.
5. With that settings, take a picture of the same scene.
6. Is there any difference?
7. Now, while you are still in manual mode, increase the Aperture number by turning the dial once (that is making the aperture smaller).
8. Keep the shutter speed and ISO the same and take another picture.
9. Any difference?
10. Now, keep the everything the same except decrease the shutter speed number by turning the dial once and take another picture.
11. Any difference?
12. Now, keep the settings in step 10 and increase the ISO setting by turn the dial once and take another picture.
13. Any difference?
You may notice that, if you increase one setting by one UNIT while decrease the other setting by one UNIT, the expose are basically the same. Don't be afraid to try, it will not hurt anything and once you play around with the above test more, you will know more about their relationship.