A mod (short for "modification") is anything that changes Minecraft's game content from what the "official" version originally was, such as the addition of new items, blocks, and mobs; changes to existing items, blocks, or mobs; or fixes to certain bugs. Mojang AB has developed Minecraft in a way which alows for extensive modding of the game client, but they do not provide support for any of the countless, third-party mods which exist online.
Effects of Mods
Mods can be used for just about anything. They can be used to change the difficulty of one's game, add more mobs, create servers easily, add blocks and items to one's game, add new worlds, and more.
Mods are normally created by a players themselves, although mods such as The Aether II have entire development teams behind them. Mods are generally found on websites such as the Minecraft Forums or on Planet Minecraft.
Installing and using a mod may have varying effects on gameplay, such as new items/blocks, new mobs or changes to existing mobs, new or changed gameplay mechanics, fixes for the game or other mods, and support for texture packs with higher resolutions. There are APIs that prevent mods from conflicting with each other, such as ModLoader.
Mods are almost never officially supported by Mojang AB, but very rarely mods get officially added to the game. An example of a mod is: McRegion, added in Beta. This mod created a more compact and faster way of storing worlds.
Players should be careful while installing mods into Minecraft, as mods will sometimes make Minecraft crash, and they can even corrupt save data if they are installed wrong. Additionally, mods that are from an unknown or little known source should be scanned for viruses before being used because it is possible that the downloaded files may contain a virus.
One example of a particular mod is the "Lucky Block" Mod, which spawns Lucky Blocks randomly in the world, bestowing either positive or negative effects. For example, a Lucky Block could spawn "Mr. Rainbow", which spawns many Sheep with various colors of Wool.
Information about Minecraft mods can be found at Minecraft Mods Wiki.
Caution about Mods
Before modifying Minecraft, make sure the current version does not crash. Back up one's worlds and also be aware that mods are unsupported by Mojang. They won't be able to help if anything happens to one's Minecraft game. When there is a new update, the Minecraft mod or mods that one has installed will not work unless one uses the version it was intended for. It is therefore recommended to delete all the modifications in the "mods" folder before installing any new mods to Minecraft, as some mods can crash Minecraft if they are used together.
In order to make a Minecraft backup, one can simply "Locate" the Minecraft.jar folder by typing in the command: /[one's computer username]/AppData/Roaming. Next, simply right-click the Minecraft.jar file. Create a new folder and put it anywhere on one's hard drive and paste the Minecraft.jar file into this new folder. Finally, rename the Minecraft.jar file to something like "Minecraft Backup".
Modpacks are just what the name entitles. They are a lot of community created mods bunched into one folder or "Pack" that usually have a certain theme of a sort. Some examples of Modpacks are CrazyCraft and the many packs in Techniclauncher.
- Download the mod files and any other mods that it may require.
- Press start and type "%appdata%" without the quotes.
- Click Roaming.
- Click Minecraft.
- Open the bin folder.
- open Minecraft.jar (may appear as Minecraft) with an archiving software (7zip, WInRAR, WinZIP etc.).
- Close Minecraft (if open).
- Delete the META-INF folder as it stops mods from working at all.
- Open up the mod (it is a folder but should appear as the archiving software's icon).
- Open up the mods it requires (same as up there ^).
- Drag everything in the desired mod into Minecraft.jar, but DO NOT drag it into one of those folders.
- Close all of those windows, then open Minecraft, and test it.
- The mod should work now.
Remember that every time Minecraft updates, it will delete every mod and its memory in the Minecraft client (only the folders will stay), and one must reinstall new mods for that version of Minecraft.
- In order for mods to work and run correctly on Minecraft, the mod creators use mod plugins such as Minecraft Forge, Forge API, etc.