If you had to boil it down, what is deep vein thrombosis?

Blood clot in a deep: Vein in your body, usually a leg vein.

Blood clot: Dvt is a serious medical problem that occurs when a blood clot develops in a vein, usually occuring in the lower extremities. The clot can break up sending small clots to the large veins and from there travel through the heart and lodge in the lung. This is called a pulmonay embolism. A pulmonay embolism is a medical emergency. Up to 20% people who suffer a blood clot to the lung can die.