There are several. You can attach laser sights, silencers, flashlights.
peripheral
A grooved receiver is a part of a firearm where the scope mounts are attached. It has grooves or rails that allow for the mounting of a scope or other optical sighting device onto the firearm for improved accuracy and precision in shooting.
In reference to a firearm, a firearm is considered loaded when there is a live round of ammunition "...in, or attached in any manner to, the firearm, including, but not limited to, in the firing chamber, magazine, or clip thereof attached to the firearm..."
It would be classed as a destructive device, not a firearm.
A bayonet.
its called a cable
Extractor
Go to device manager and you see all the devices attached and their status and properties
I believe you are referring to "cartridge." The cartridge is the entire assembly of the bullet, primer, powder charge, and casing.
Sight
The EJECTOR. The EXTRACTOR withdraws the empty case from the chamber, but the EJECTOR throws it out of the firearm.
I believe it is to assist in the removal of the device