Integration is a module of ProjectRed. It adds extra logic gates to Minecraft. These gates, when taking in a signal from either default Minecraft redstone dust or the relevant wire will perform operations on or set outputs based on the signal.
Fabrication is a sub-module of Integration, that adds the IC Gate and its associated blocks.
Integration adds many logic gates to the game. A logic gate is a small tile, much like the Redstone Repeater. Its purpose is to squeeze the functionality of a large redstone machine into a small block. And since logic gates are multiparts, they can be covered with micro blocks, or even share a block space with other logic gates.