ACE inhibitors are a class of medications that block the angiotensin-converting enzyme, leading to decreased production of angiotensin II, a potent vasoconstrictor. This results in vasodilation, reduced blood pressure, and decreased workload on the heart, making them essential in managing hypertension and heart failure. A key example is lisinopril, which can cause a persistent dry cough as a common side effect due to increased bradykinin levels.