Auto and Run can be useful if you want to make a lot of changes to the
control settings at once but don't want to wait for Fractals to re-run
all of the calculations every time that you change one control. Fractals
can tie up your computer for quite a long time while doing the calculations
and after enough repetition it could get to be annoying.
When Auto is selected, Fractals re-calculates and plots the image for
every control change. But when Auto is de-selected the last preview
image is frozen. If you click the Run button when Auto is de-selected
the calculations will be run one time and then the preview image is
frozen again. The calculations will also be repeated if you click Run
with Auto selected, but there's not much reason to do that.
Changing Auto from de-select to select also runs the calculations one
time so that you don't have to click the Run button too when going back
into Auto mode.
For example you may want to stop the calculations temporarily by
de-selecting Auto so that you can set up the controls to match one of the
samples from the Fractal Gallery. Then whey you have everything ready you
can select Auto to start the calculations running automatically again
and start experimenting with the controls.