Bailout is the value which is checked for each point of the orbit if the point is far enough from the complex zero point in the current iteration. If the point is far enough, then the iteration immediately stops and the starting point on the screen will be painted with a given colour, depending on the fractal type and many other settings.
For the Mandelbrot set this value is 4. Other fractal types usually have the same bailout value. For most fractals many bailout values give more or less similar output. E.g., for the second order Mandelbrot set one can prove that the sequence |z| (z:=z^2+c) tends to infinity if and only if |z|>2 for some element z of this sequence. In XaoS program, Bailout value is the square of this 2, i.e. you can change this to any value greater than 2 for similar results.
Other fractal types may use other bailout values. The default is 4 for each types.
Available as: menu item, command line option, command