Atherosclerosis is a disease where plaque builds up inside arteries. It is caused by inflammation in the arteries due to risk factors like high cholesterol, high blood pressure, smoking, and diabetes. Over time, plaque hardens and narrows the arteries, reducing blood flow. This can lead to complications like heart attacks or strokes if a plaque ruptures. Doctors use tests like ultrasounds and angiograms to diagnose atherosclerosis and determine if the arteries are blocked. Treatment involves lifestyle changes and medications to control risk factors and blood pressure. In severe cases, procedures like angioplasty may be needed to open blocked arteries.