A gun receiver is the part of a firearm that houses the internal mechanisms which are responsible for firing the weapon. It is the frame or body of the gun that holds all the other parts together. A gun receiver is typically made from steel, aluminum, or polymer and is generally considered to be the firearm itself under most state and federal laws. The receiver is what gets serialized when a buyer purchases a gun, and it is also what needs to be transferred if a gun is sold or gifted. When it comes to repairing or modifying a firearm, most of the work will be done on the receiver. This includes things like adding optics, installing new triggers, and changing out stocks. As such, it's important to understand what a gun receiver is and how it works in order to properly maintain your firearms.