In the most simple terms, they are the same thing. An embolism is the sudden blocking of a blood vessel. It can be caused by a bubble of air, blood clot, or piece of fat.
Pulmonary embolism is blockage of an artery to the lungs. It can be a blood clot that has broken off from the leg and traveled to the lungs. A blood clot that forms in the arms ar legs is called a deep venous thrombosis (DVT).
Doctors try to anticipate blood clots. Prevention and early detection are the keys to avoiding death from pulmonary embolism.