Leukocytes, also known as white blood cells, are a crucial component of the immune system responsible for defending the body against infections, diseases, and foreign substances. They are produced in the bone marrow and circulate throughout the body via the bloodstream and lymphatic system. Leukocytes are highly diverse and can be categorized into different types, including neutrophils, lymphocytes, monocytes, eosinophils, and basophils, each with specific functions in immune responses. They work together to identify and destroy pathogens, remove damaged cells, and regulate immune reactions. Leukocytes play a vital role in maintaining the body's overall health and protecting it from harmful invaders.