Modeling is a way to represent a real-world system using software, hardware, or a combination of both. If the software components of this model are driven by mathematical relationships, the model can be simulated under various scenarios to verify that the system is represented correctly and that it properly responds to input signals.
Modeling and simulation are especially valuable for testing conditions that might be difficult to reproduce with hardware prototypes alone, especially in the early phase of the design process when hardware may not be available to test. Iterating between modeling and simulation can improve the quality of the system design early, thereby reducing the number of errors found later in the design process.
A common representation for system models is the block diagram, which can represent systems like controls, signal processing, communications, and mechatronics. To learn more about modeling and simulation with block diagrams, see Simulink.