In locksmith terms
An emergency key, sometimes called an emergency blade or insert key, is the mechanical blade hidden inside most smart fobs. It releases with a button or slide and fits a physical lock cylinder, usually on the driver's door, that may be concealed behind a small cap. Its job is manual entry when the fob battery or the vehicle battery is too low for keyless entry.
The emergency blade unlocks the door. On a push-to-start vehicle it does not start the engine on its own, because starting still depends on the immobilizer recognizing the fob's chip. It is purely a way in, not a way to drive off.
In plain English
Your smart fob almost certainly hides a small metal key inside it. Pop it out and you can unlock the door by hand if the fob stops responding. It is the backup for the moment the electronics will not cooperate.
Getting into the car is what it does. Starting the car still needs the fob, so the blade is about access, not ignition.
What to do if yours is missing or uncut
Some fobs ship with a blade that was never cut to the lock, and sometimes the blade gets lost. A locksmith can cut an emergency blade to your specific door lock so you always have a manual way in. It is inexpensive peace of mind, especially before a dead-battery surprise.
Still have a key or fob question?
Tell us your year, make, and model and we will confirm exactly what your vehicle needs before we head out.