Narrator
The narrator, presumably the voice of Petrarch himself, is present in all of his sonnets. In some of them the narrator addresses a more general audience, but in many he speaks to or about a specific woman he loves.
Audience
The audience is the unspoken listener that Petrarch's narrator addresses in the sonnets. As a character, it is able to be interpreted as the reader or a specific person the narrator is addressing who they may know more intimately, such as a friend or a lover.
Laura
Someone beloved of the narrator who has likely passed away. Although Laura is dead, the narrator still feels a strong love for her and hopes to join her in heaven one day.
"Her"
A love to whom Petrarch refers in many of his sonnets. Often the woman of whom he speaks does not return his love, causing the narrator of the sonnets to despair.