Junction boxes are metal or plastic enclosures used as housings for wiring connections. The connections within are called branch circuits and usually represent the end of a conduit run. Junction boxes make wire access easy, since all one must do is remove the covering to make alterations, repairs, or additions to a conduit. Junction boxes also protect wiring from the elements or environment, which can sometimes be corrosive or otherwise harmful to wiring material. Finally, junction boxes protect wiring from unwanted tampering, whether malicious or unintentional.
Junction Box Wiring Basics
Essentially, a junction box houses wire connections in order to split off power from a single source to multiple outlets. For instance, a distribution box might contain one wire power source that is connected through multiple wires to power several different lights.