It's called a "trailer" because, in the old days, a short movie clip of a coming attraction was shown after the feature film. Now, these clips are usually shown as "previews" before the feature film. But in the movie industry, the term "trailer" is still used.
So here is the trailer of the MCS film, CAESAR, now being filmed by the high school and middle school students.
I'm impressed with the techniques for using the printed word. Nice job!