You'll study that later. These are pretty straight forward. Look at the Erythroid Series. Here's where the action is, but you'll see it's pretty straight forward as well. The leukocytes are part of our immune defense system.
Granulocytes inlcude the neutrophils, eosinophils, and basophils.
It shouldn't surprise you to learn that their cytoplasm is often filled with granules. Make sure you learn the neutrophil. Eosinophils are involved in allergic reactions and parasitic infections. Some think that the mast cell is derived from the basophil. Just remember that the basophil circulates and the mast cell is found in peripheral tissues.