[Note: Before using mods you should know about Mods.]
A mod, or modification, is the culture of allowing users and outside developers to customize video games. Mods may include new items, characters, stories, levels, art, music and game modes. Extensive mods may invent new elements of gameplay or change the behavior of game engines. In some cases, mods also fix bugs.
A mod (short for "modification") is an alteration that changes some aspect of a video game, such as how it looks or behaves. Mods may range from small changes and tweaks to complete overhauls, and can extend the replay value and interest of the game. The Internet provides an inexpensive medium to promote and distribute user created content like mods, an aspect commonly known as Web 2.0. Video game modding was described as remixing of games and can be therefore seen as part of the remix culture as described by Lawrence Lessig. Mods have become an increasingly important factor in the commercial success of some games. Developers such as id Software, Valve Corporation, Mojang AB, Bethesda Softworks, Firaxis, Crytek, Creative Assembly and Epic Games provide extensive tools and documentation to assist mod makers, leveraging the potential success brought in by a popular mod like Counter-Strike. In cases where mods are very popular, players might have to clarify that they are referring to the unmodified game when talking about playing a game. The term vanilla is often used to make this distinction. "Vanilla Battlefield 1942", for example, refers to the original, unmodified game. As early as the 1980s, video game mods have also been used for the sole purpose of creating art, as opposed to an actual game. This can include recording in-game actions as a film, as well as attempting to reproduce real-life areas inside a game with no regard for game play value. This has led to the rise of artistic video game modification, as well as machinima and the demoscene.