What is Anemia ?. Anemia is a condition that develops when your blood lacks enough healthy red blood cells or hemoglobin. Hemoglobin is a main part of red blood cells and binds oxygen. If you have too few or abnormal red blood cells, or your hemoglobin is abnormal or low, the cells in your body will not get enough oxygen. What is White Blood Cells?. White blood cells are an important component of your blood system, which is also made up of red blood cells, platelets, and plasma. ... White blood cells, also called leukocytes, are essential for good health and protection against illness and disease. Think of white blood cells as your immunitycells.