A key fob is a small object that contains the remote keyless system in an automobile.
A small object, usually made of leather or plastic and about the size of a pocket watch, that houses the receiver inside. This can be attached to a belt loop or on a chain for easy access.
Information to include in answer: The term “remote keyless entry” is industry-specific and means any type of wireless remote entry device for an automobile door lock system. It operates by sending coded information from either at close range or from up to 30 feet away with the help of radio waves emitted through antennae — allowing car drivers to unlock their car if they are outside of it but too far away to reach it physically.
Key fobs are the most common device today, but earlier systems used magnetic key switches on motors in which a proximity switch turned on an electromagnet (attached to the door lock) when you got within range of it; you would then unlock your car by sticking your regular key into this magnet.