You will receive 15 random names for plagues, diseases and other epidemics. All names are in a kind of tag, just like how the bubonic plague, for example, is called the Black Death. Aside from the Black Death, real-life epidemics don't all that often have the same names. They are most mostly called after the location in which it has taken place or begun, so it could be a choice if you want to remain closer to real life. But if the root is vague and its scope is broad, the surnames work well, particularly because it sounds more ominous. There's plenty to choose from, however, most of the names have a common subject of death, suffering and just general misery as predicted by names associated with widespread diseases.
To generate another 15 random names you just have to press the button. With every click 15 new names are generated.