The X-Y Rotation control rotates the image around the center point in the
X-Y plane which means as you look at the image straight on. The Rotation
range is 0 to 359 degrees going clockwise so the image can be oriented
to any possible angle.
There are some issues involving the Position
and Compression controls that Fractals has to
compromise on. This can cause the other controls to appear to go in
the wrong direction sometimes. See the details of those controls for
more information on what to expect.
Other than that, X-Y Rotation is pretty straightforward. Here's an
example that shows how valuable the effect can be.
The image on the left was created with the same settings as
Demon in the Fractal gallery.
As you can see in the image on the right, without rotation the poor
demon falls down and would be very difficult to find lurking in
the Mandelbrot set.
X-Y Rotation = 270
X-Y Rotation = 0