Peripheral Arterial Disease (PAD) is a common circulatory problem where narrowed arteries reduce blood flow to the limbs. It is usually caused by atherosclerosis, which narrows the arteries through plaque buildup. Common symptoms include intermittent claudication pain brought on by walking. Diagnosis involves tests like the ankle-brachial index which compares arm and ankle blood pressures. Treatment includes lifestyle changes like quitting smoking, medications to improve symptoms, and potentially surgeries like angioplasty or bypass if lifestyle changes and medications are not effective.