The discussion revolves around a C programming issue related to the definition and instantiation of a struct, specifically the `sensor_data` structure. The user encounters multiple definition errors due to the instantiation of the struct variable `Sensor` in the header file, which leads to global variable conflicts. It is clarified that struct definitions should be in header files, while instantiations should occur in source files to avoid such errors. The conversation also touches on the proper use of pointers and function prototypes when passing struct data, emphasizing that pointers should be used to modify struct data within functions. Ultimately, the user resolves their issues by adjusting the order of operations in their code and removing unnecessary global definitions.