In "Her," all computers are controlled with touch, voice, and gestures - keyboards or mice are relics of the past.
While I don't want to ruin the plot for anyone, I will say that the story of Theodore Twombly (wonderfully played by Joaquin Phoenix) falling in love with his computer's new operating system - a futuristic take on a Siri-like computerized assistant voiced by Scarlett Johansson - is incredibly romantic and probably the best science-fiction film released this decade.
What makes it so great as a piece of sci-fi is its realistic, subdued take on the technology of tomorrow. Set in what we can estimate is at least a decade in the future, the film presents a future where Siri, the Xbox's Kinect motion sensor, and Google Glass are no longer novelties but commodified technologies - like the mouse today, they've been around for a while and no one marvels at the fact that they exist.