Research part 2 :)

The term 'trailer' originates from the earliest forms when they were played at the end of the film, now they are more commonly known as 'teasers' or 'previews' for what is to come. Over the years the use of trailers has become predominantly more open, with it ranking 3rd in the most watched videos on the Internet, after news and user-created videos. The first trailer was shown in 1913 by Nils Granlund as a promotion for the musical The Pleasure Seekers, previewing at the Winter Garden Theatre on Broadway. They were mostly created by the National Screen Service up to the late 50's, often showing a key screen with the story plot described in text, along with a stentorian voice over, as is still common in trailers to date.
The 'New Hollywood' in the 1960's brought a change in trailers, removing the text and using quick-editing on montage trailers, among the trendsetters was Stanley Kubrick with films such as Lolita.