How does nitroglycerin work to relieve angina?

Nitroglycerin relieves angina primarily by venodilation (reducing venous return and cardiac preload) and coronary artery vasodilation (improving myocardial oxygen supply), both mediated through nitric oxide release. By reducing preload, nitroglycerin decreases myocardial oxygen demand. Coronary vasodilation improves blood flow to ischemic myocardium. The mechanism involves NO-mediated activation of guanylyl cyclase, increasing cGMP, and ultimately causing smooth muscle relaxation. This question appears to be a near-duplicate of Q10 but with simpler options. Both are retained as they represent a slightly different framing of the same concept.