  The paper discusses the main ideas of the chaos theory and presents mainly
the importance of the nonlinearities in the mathematical models. Chaos and
order are apparently two opposite terms. The fact that in chaos can be found a
certain precise symmetry (Feigenbaum numbers) is even more surprising. As an
illustration of the ubiquity of chaos, three models among many other existing
models that have chaotic features are presented here: the nonlinear feedback
profit model, one model for the simulation of the exchange rate and one
application of the chaos theory in the capital markets.
