The Configurator is a tool added by Mekanism that allows for configuration of Mekanism's various machines and pipes.
Machine Inputs and Outputs
While holding a Configurator and mousing over a machine's sides, the color of the side will be shown as it is configured for the machine.
Cables, Pipes and Tubes
Universal Cables, Logistical Transporters, Mechanical Pipes and Pressurized Tubes can be configured using a Configurator. When one of these are exposed to a redstone signal they will detach from surounding machines or pipes, allowing for a "switch". This behavior can be disabled by right-clicking with a Configurator on the pipe.