Final answer:
An embolus is a thrombus that has broken free and entered the circulation; when it causes an occlusion, it's termed an embolism, which can lead to life-threatening events such as pulmonary embolisms, heart attacks, or strokes.
Step-by-step explanation:
When a thrombus, which is an aggregation of blood components such as platelets, erythrocytes, and white blood cells, gets dislodged from the blood vessel wall, it becomes an embolus, moving through the bloodstream. If the embolus becomes trapped in a blood vessel, it can cause an occlusion, resulting in an embolism. This is a medical emergency because the embolism can block blood flow to major organs leading to severe consequences such as a stroke, heart attack, or pulmonary embolism (PE). Especially in cases of deep vein thrombosis (DVT), there's a risk that part of the thrombus might break away, form an embolus, travel through the circulatory system, and potentially cause a PE, which can interrupt the blood flow to the lungs and have serious or even fatal outcomes.