Industrial Craft 2 adds many machines to Minecraft which help the player to automate and increase efficiency. It also includes many features other than machines, such as plant Cross Breeding, new blocks, and new Achievements.
The machines and generators in Industrial Craft 2 deal with their own form of energy, called Energy Units, or EU.
It is important to note that in order for Tekkit to work correctly on a server, the server owner must op the mod itself, by typing '/Op [industrialcraft]'. This is because the mod needs permission to interact with the environment.