This is some type of surface on which guitar effects pedals are placed conveniently to have everything in one location rather than spread out all over the stage (when playing live, of course). These range from simple, homemade versions (like an old suitcase or briefcase) up to the most sophisticated versions built by manufacturers which may even include an integrated power supply for all the devices to be plugged into. The only down side to this approach is the possibility of hum and ground loops, but this has become quite rare as manufacturers have constantly improved their products. If you decide to build your own, keep in mind that Velcro is the best way to quickly put effects into place, particularly if you may be changing your setup on a fairly regular basis.