Simply put, Applied Energistics, also known as Applied Energistics 2 and AE2, is a technology mod most notable for the ME System: A matter-energy conversion storage system. The main resource for AE2 is Certus Quartz. To start off AE2, throw a redstone dust, certus quartz crystal, and nether quartz item into a pool of water. This should give two Fluix Crystals.
Applied Energistics will take a large amount of power; each part of the ME System will require power for each part. For example, a single Glass Fluix cable requires 2 RF a tick. Note that you can not simply hook up the ME System to a power cable; it requires an Energy Accepter attached to the power supply to obtain energy. While the Engineer gives a slight tutorial on the ME System, it lacks depth and thorough explanation. You do require the presses he gives you to start, so a pickaxe or other tool capable of mining Skystone is necessary.
The Thaumcraft expansion Thaumic Energistics combines Thaumcraft mechanics with ME System devices; an Arcane crafting terminal to use arcane crafting in the system and digital Essentia storage being two primary focuses.