>>4434208
You'll understand Manual by doing this:

>babies first footsteps
Use your preferred mode (e.g Aperture)
Set ISO to 100
Now you must maintain the wished aperture and get used to adjusting the exposure compensation with your wheel (which is actually adjusting the shutter speed)

Once you are attuned to this soon you will choose to adjust ISO based on surrounding and creativity (for me mostly dark/low light environments where I manually adjust to 400 - 800 if I want aperture and want shutter speed to stay at desired levels while also getting good exposure)