Thrombosis is the formation of potentially deadly blood clots. Blood clots can form in the artery (arterial thrombosis) or vein (venous thrombosis). Blood clots in the arteries cause heart attacks and strokes. Blood clots in the veins can lead to death due to breaking off and blocking the blood supply to the lungs:
Deep vein thrombosis (DVT) is when blood clots in a deep vein (most often the leg)
Pulmonary embolism (PE) occurs when a blood clot breaks loose and travels to the lungs
Collectively, DVT and PE are known venous thromboembolism - VTE.