This category is used for all modifications (mods) of the games which are not from official sources. Mods can add new content, change some content already existing, fix bugs and restore content removed from the final retail version of the games or give you new ways to cheat through the games.
Mods are completely optional and it's recommended to finish the game at least once in an unmodded form before adding them, as they may change the gameplay experience for the better or the worse.
Here are some sites that provide various mods
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