There are two main use cases for Simulink.

The first one is in the academic research world where Simulink is used to simulate multidomain dynamic systems. Typically, Simulink is used in a continuous-time environment with variable step-size implicit solvers; the main scope of the simulation is to reproduce the behavior of a real system in order to predict the answer to the applied stimuli.

The second one is in the automotive, aerospace, avionics, and the defense industry where Simulink is used to build models for real-time, safety-critical, embedded targets with many people involved in the specification, development, and testing phases. The main scope of the simulation is to find and correct bugs in order to produce (through the appropriate code-generation software) a final C code to compile in the target processor. The simulation solver used in this environment is the fixed-size step explicit one, and the model doesn't contain any continuous states.