This dimmer takes the full bandwidth of a house hold circuit and can dim it accurately from 0 -100%.  It has a digital readout of the percentage on the front.  This helps to bring repeatability to your setups.  You simply run a U-ground extension cord from your wall plug to the dimmer, and then plug your U-ground fixture into the other side of the dimmer.  Physically the unit has end plates to allow it to be permanently mounted.  We tie a rope through it to let it hang off a light stand.