In the old stories of ancient Greece, Hades is the land of the dead — the place souls go after they die. It is thought of as a shadowy world under the earth. The god who rules that land is also called Hades, so the same name is used for the place and for the ruler. This sense is the land. Though actually, English speakers often treat Hades as another word for Hell. That is later, and it comes from church language and later books. In the Greek stories, Hades is not mainly a place of fire and punishment for bad people. It is where the dead live, good and bad. You meet the word in myths, school books, films, and games, not in everyday talk. Write it with a capital H: it is a name.