Pluto (Ploutōn) was a name for the ruler of the underworld. Hades was the name of the god and the underworld itself.
He received the rule of the underworld in a three-way division of sovereignty over the world, with his other two brothers Zeus ruling Heaven and Poseidon the Sea.
He abducts Persephone to be his wife and the queen of his realm.
The names Ploutōn and Plutus were frequently conflated.
Plutus was a god of wealth, because mineral wealth was found underground, and because as a god Pluto ruled the deep earth that contained the seeds necessary for a bountiful harvest.
Ploutōn became a more positive way to talk about the ruler of the underworld. Mystery religions and philosophical systems popularized his name.
Pluto (French Pluton and Italian Plutone) is commonly used as the name of the ruler of the underworld in subsequent in Western literature and art.