I take it that a system is a network of heterogenious components all of which can be interactive with an influence on each other.
A system is dynamic, it's constantly changing, though may be in an equilibrium of balancing forces, a limited cycle, a chaotic cycle or completely random.
Read with SystemsDynamics
See also :
MIT teaching Systems Dynamics and Systems Thinking : http://www.uni-klu.ac.at/~gossimit/eng/sdyneng.htm