The test involves collecting stool samples, which are then analyzed for the presence of blood. There are two main types of FOBT: the guaiac-based FOBT (gFOBT) and the fecal immunochemical test (FIT). The gFOBT detects heme, a component of hemoglobin, while the FIT specifically targets human hemoglobin proteins. Both methods have their advantages and limitations, and the choice between them often depends on the specific needs of a screening program.