Pulmonary embolism (PE) is a blockage in the pulmonary artery caused by a thrombus, typically originating from the venous system, leading to reduced blood flow and oxygen levels in the lungs. Risk factors include cancer, family history of clots, obesity, and prolonged immobility. Symptoms often include sudden shortness of breath, chest pain, and dizziness, and management strategies involve anticoagulants, oxygen therapy, and possible surgical interventions.