A movie is a film that you watch at a theater or at home on your TV, laptop, or tablet. Movie is short for "moving picture," which was pretty exciting in the late 1800s.
You can rave about your favorite movie — whether it's "Citizen Kane" or "The Lion King" — and you can also talk about "the movies," or films in general and the industry that makes them. You might dream of working in the movies, for example. Before about 1912, movies were called "motion pictures." Movie is a shortened form of the phrase, which some people abbreviate into the more old-fashioned sounding "pictures."