What is system modeling? or for short systems model

I need a short definition of what systems modeling is, because I can't find any definition at all online, help as soon as possible, and thanks much

If you're asking about computer modeling systems, they are methods of applying the variables affecting a problem and stepping the software through it to see how it behaves when different solutions are applied.

An example would be a program used to test trading systems for the stock market. You would load all of the historical prices in the computer and step by step apply the algorithm as a trader would do it, then compare the profit for each test to choose the best system.

It's essentially a form of "reverse engineering."