Baby I. It's a song about falling in love with a new person. It's about when everything about a relationship is new and exciting, or as Ariana would say: "you get all tongue-tied and twisted." The song is about that giddiness you feel when in love, and has a video and dancing to match that feeling.
Not only does the video have dancing, which it totally does, the dancing is actually very skilled interpretive dance. Ariana sings about being tongued-tied and twisted and she is very often twirling around, in love of course. Yes, occasionally Ariana is sitting while her troupe dances behind her. This is actually a brilliant decision. Ariana is literally floored, and unable to move while her emotions dance around her. She does get her act together, dancing on the streets and doing a hopscotch like jig outside a building at night (and let's not forget her dead-on hose party dance at the end), but with that same effortless breezy and light touch that's reflected in the song. Baby I... think Ariana pulled off the dancing for this video.