1) The Black Death was a plague pandemic that devastated Europe from 1347 to 1351, killing an estimated 30-60% of Europe's population.
2) The plague was caused by the bacterium Yersinia pestis, which was carried by fleas living on rats. When rats died, fleas sought new hosts in humans, spreading the plague.
3) The consequences of the Black Death were severe - it killed around half of Europe's population and drastically changed societal and economic systems throughout the continent in the aftermath.