A Differential White Blood Cell Count is a laboratory test that measures the percentage of each type of white blood cell (WBC) in your blood, providing crucial insights into your immune system's health and detecting various conditions like infections, inflammation, and hematological disorders. It helps in diagnosing the underlying causes of abnormal WBC counts by distinguishing between different types of leukocytes, such as neutrophils, lymphocytes, monocytes, eosinophils, and basophils.