Leukocytes, commonly known as white blood cells, are a crucial component of the immune system, helping the body fight infections and other diseases. They are produced in the bone marrow and circulate throughout the bloodstream and lymphatic system. There are several types of leukocytes, including neutrophils, lymphocytes, monocytes, eosinophils, and basophils, each with specific functions in immune response and inflammation. Their levels can indicate health status, with variations often signaling infection, inflammation, or other medical conditions.