A Press-Kit is what goes out to the different publications and sites, along with artbooks etc, and they normally contain game artwork in .psd and high res .jpg, system pics, logo's, screenshots of upcoming titles, some contain midi music and trailers to, some also contain other media such as calendars etc.
This kits contents:
An overview of the main menu and what games are covered can be seen here:
From there you can go back to the main menu, next game, previous game or view asets for the current game, the assets for each game are screenshots, High res art work and high res logos, mostly in .jpg but theres a few .psd's to. And a release/game synopsis.
.7z/Capcom E3 2005 (Press-Kit CD)/Capcom E3 2005 (Press-Kit CD).jpg){kind=link}