There are a few different game trailers available online for Age of Empires 3. This particular trailer is from GameTrailers.com
and is in High Definition Windows Media format. It is available in both Quick Time and Windows Media formats as well as in HD and non-HD with the only difference being the file size(and picture quality).
The Age of Empires 3 game trailer
begins showing various animation sequences that somewhat set the background for the game as it then moves into showing some actual game-play and combat situations that are in store for the game. It is approx 1:30 inlength and is well worth the short download time in order to view the excellent graphics. There is also an game-play only trailer avialble at GameTraielrs.com that does not include any sound.