Immortali means "immortal" or "undying." It's a strong, evocative word that suggests something lasting forever, beyond the constraints of time.
In the song, the lyrics
"Photo" is about wanting to freeze a perfect moment with someone and make it last forever, the way a photograph does.
The verses paint an intimate scene: her body is in the room, but her mind and heart are entirely with the person she loves. She wants to slow time down, forget the clock, and hold on to this feeling before it can slip away.
The chorus is the heart of the song: like a photo, we are immortal. Being fully present with someone, she says, is its own way of stopping time. She calls this person her revolution, her only season, the thing that heals whatever hurts. By the end, she trusts that if he stays close, whatever comes next will be worth it.