Global, Gamedata, and other files control many aspects of the game, too many to list.
Files beginning with "u" and "r" are uniform files. The first being home, away, and alternates whereas the second are for retro jerseys and other special uniforms.
Files beginning with "s" are stadium files, "f" for floor files, and "logo" files are obviously for logos.
To find what number (ex. uh005.iff) cooresponds to what team, please reference this thread;
viewtopic.php?f=150&t=88186
"png" files are player CF files, they contain that player's cyberface texture, tattoo textures, and other things that are specific to that player.
To find a specific player's number, reference this thread;
viewtopic.php?f=154&t=92751