IV therapy involves administering fluids directly into the bloodstream through a peripheral or central vein. It can be used to restore fluids and electrolytes, administer medications, provide nutrition, or perform transfusions. Close monitoring is needed to prevent complications like infiltration, extravasation, phlebitis, infection, and fluid overload. The nurse must properly prepare the IV site and equipment, select the best vessel and solution based on various factors, and maintain sterility throughout the procedure.