Overall, it's about realism-inspired technology:
Instead of glowing red tubes, it offers actual, hanging powerlines.
Instead of one block that magically spits out dusts when ore is put in, it offers a crusher, a big multiblock (5x3x3) that features rotating wheels and spits out particles as it breaks the ore.
Instead of a Laser that turns power into magical light and ores, it offers an Excavator, another massive, resource intensive, multiblock (3x7x8) which digs ores out of the ground with a big rotating bucketwheel.
IE is about making tech mods more balanced and more pretty, and adding its own twist by going for retro-futurism (think BioShock, Order 1886, SkyCaptain and the World of Tomorrow) rather than clinical white+grey future cubes.
It uses the RedstoneFlux API, known from Thermal Expansion, BuildCraft, EnderIO and other mods, but can be played fully standalone. Unlike other mods, IE does not use powertransfer via lanes of blocks, but instead via cables spanned between connectors.
It also allows transport and conversion of IC2's EU =P
The mod features Power Generation in forms of waterwheels, windmills, biodiesel and more and many of its machines are multiblocks!
For all your documentation needs, you should look into this mods ingame documentation, the Engineer's Manual, crafted with a book and a lever.