What was the plague?

"While the coronavirus COVID-19 changed the world in 2020, it still isn't the largest and deadliest pandemic in history. That title is held by the Plague. This disease, also known as the 'Black Death,' spread throughout Asia, Africa, and Europe in the fourteenth century and claimed . . . 50 million lives by the time it officially ended. [The] author . . . takes readers back to these . . . years, explaining just how this pandemic began, how society reacted to the disease, and the impact it left on the world"--Amazon.