For those that don't know, Dante's Inferno is actually one of three books in "The Divine Comedy" from fourteenth-century poet Dante Alighieri. The book follows Dante as he progresses through the layers of hell. The game adds in rescuing Beatrice to give players more meaning to go through hell.
Along the way, the poet Virgil follows Dante on his quest and gives him information. In the game, this information is on new areas, upcoming bosses and more. Virgil can usually be spoken to multiple times in an area, and will give more detailed information about what's coming up and sometimes even give Dante a relic, which will be discussed later.