The phrase "trailer reel" refers to a collection or playlist of movie trailers. It is like a compilation of short videos that give a preview or a sneak peek of upcoming movies. Full definition
A trailer for Perfect Creature and the Fox Horror trailer reel start on insertion. (filmfreakcentral.net)
Rounding out the sparse package, the Dimension Cutting Edge trailer reel (featuring clips from various Dimension titles like From Dusk Till Dawn, Scream, Scary Movie, and so on) and previews for the Dimension titles Below, Undisputed, Asunder, and the ponderously - titled Wes Craven Presents Dracula II: The Ascension. (filmfreakcentral.net)
Extras: Actor and director filmographies, Film notes, Theatrical trailers, Teaser trailers, World cinema trailer reel. (movie-gazette.com)