The PEController has two cores that need to work together, so they have to share information and memory. In the "shared_memory.c" file, there is a variable called sharedData which holds the data that both cores need to share. This data is stored in SRAM4 so that both cores can access it. The shared data includes things like the ADC settings, ADC results, and other important control information. By using this shared data variable, the system can control its different states effectively.