Hormones are chemicals released by cells, glands or organs that can affect the cells in other parts of the body of an organism. Generally it can be classified based on its solubility: water and lipid (fat) soluble hormones. Both act as chemical messenger to other parts of the body which signals for a certain action either to prevent something to happen, promote growth; induce action for repair or maintenance. Both types also have receptors or receiver of the signals.
Water soluble hormones are hydrophilic. It cannot pass through a membrane since it has fatty component. Instead, what is does is that it binds on the surface of the target cells. Eventually, chemical reactions due to the binding on the surface can now trigger activity inside the cells.
Fat soluble hormones are lipophilic. This means that it can pass through the fatty membrane thus can allow the reaction inside the cell. The binding of the hormone with the receptors happens inside the cell thus forming the hormone-receptor complex. This complex now can move across the nuclear membrane and can binds to DNA sequences thus affecting the protein synthesis and eventually the cellular metabolism.