Mods

A Mod (short for modification) is software created by a third party group (such as a mod team) or company that modifies one or more aspects of an existing game. These aspects may include, scripting, code and new maps. Aesthetic aspects such as replacement models, textures and sounds usually aren't considered to be 'mods' when released on their own. A total conversion is a mod that runs on the engine of the game it's based on and shares much of it's code, but otherwise replaces almost everything else and uses few or none of the original game's assets (such as textures or models).

Some mods make only relatively minor visual and gameplay changes (SMOD, for example) while others are total conversions which drastically differ in design and setting (Dystopia)

Many Half Life 1 and Half Life 2 Mods are listed at the site Mod DB. Many of these Mods can be downloaded for free.

A large number of mods based on the Source engine are in the works and quite a few have been completed or are in beta stages.

Some original mods, like Counter-Strike, Team Fortress, Day of Defeat, and - recently - The Ship, have been 'adopted' by Valve and made into commercial games.

Well-Known Mods

 * Garry's Mod
 * The Survivors
 * 007: Source
 * Obsidian Conflict
 * Dystopia
 * SMOD
 * SMOD Tactical
 * Zombie Master
 * MINERVA
 * Black Mesa Source
 * Pirates, Knights and Vikings 2
 * HL2: Capture The Flag
 * Plan of Attack
 * Source Forts
 * Syngergy
 * Empires
 * Battlegrounds 2
 * Eternal Silence
 * The Hidden: Source
 * Zombie Panic: Source
 * Movie Battles: Source
 * Insect Infestation
 * Half-Life 2: Riot Act
 * Combine Destiny - Website:
 * Combine Destiny 2
 * Special Forces: Source