A fractal is a mathematical set or concrete object that is irregular or fragmented at all scales...

If you look at coastlines, if you look at that them from far away, from an airplane, well, you don't see details, you see a certain complication. When you come closer, the complication becomes more local, but again continues. And come closer and closer and closer, the coastline becomes longer and longer and longer because it has more detail entering in.

There are very complex shapes which would be the same from close by and far away.

Beautiful, damn hard, increasingly useful. That's fractals.

In fact, I barely missed being number one in France in both schools. In particular I did very well in mathematical problems.

The techniques I developed for studying turbulence, like weather, also apply to the stock market

If you assume continuity, you can open the well-stocked mathematical toolkit of continuous functions and differential equations, the saws and hammers of engineering and physics for the past two centuries (and the foreseeable future).