Fractals are generated by iterating a function…or by applying a feedback loop to a system.
(Iterating a function means that you take the output from the equation and feed it back into the equation.)
A “Fractal” then, is what “emerges” from these feedback systems. We call this the “emergent property” of the system.
Usually fractals are displayed as pictures where the numbers coming out of the fractal equation are mapped to colours and positions on a graphics display, however, fractals can also be represented as sounds or as 3-Dimensional models. It’s up to the fractal "practitioner" to decide how to present their data.