This picture depicts a famous Canto from the Inferno. Virgil takes Dante into Hell, and there he meets the souls of those being punished for sexual sins. They are in a high circle of Hell, because St. Thomas Aquinas (whose theology inspired Dante) believed that sexual sins were the least serious of sins. (Dante places Brutus, Cassius, and Judas in the deepest circle of Hell for the sin of betraying their masters.)
Francesca da Ramini was an actual historical figure, and a contemporary of Dante. She was married to seal a political alliance between her father’s family and her husband’s family. Her husband was crippled, and she took Paolo as her lover. When her husband Giovanni discovered the two of them in bed together, he killed both of them. Virgil and Dante meet both of them in Hell, where they are being punished for adultery.
I love the way the painting captures both the eroticism and the tragedy of their story.