Its about the story of a young (later a bit old) doctor in his quest to find and kill the "monster" that he once saved whilst proving his innocence to the series of events that happened within the story. Ironically he is torn between the responsibility of fixing his mistake and as a doctor, saving precious lives.
The series is intricately plotted and weaved together to deliver a solid story and remarkable characters. And unlike normal anime that is set in a fictional world, Monster is set on real life places in the world and tackles several historical plots and events and incorporated it in the story.
2) A big-ass thing that's in a shitload of really bad horror movies, used to scare people.
Godzilla is a monster