Some robots are AIs, but not all of them -- so far as I know, I'm not overly familiar with robots -- and not all AIs are robots. In my world they take the form of ships and space stations. They are sentient, and very smart, and honestly some of the very best people in the universe.
Station is the AI that looks after the Garden, as well as the rest of Athoek Station, on which it's located. She is the station, in a very real sense. There are consoles and sensors throughout the ship for Station to keep track of things, and to be able to speak to you. She'll also be the main one providing you with information about the Garden and its plants, since she knows much more than Breq and I do.