In locksmith terms
Cloning copies the data from a working transponder chip onto a new blank chip so the duplicate carries the same identity. Because the clone presents the same code the car already trusts, the vehicle does not need to be told about the new key. That makes cloning fast and possible without putting the car into a programming mode.
Cloning works on many earlier and mid-generation transponder systems. Newer systems that use rolling or encrypted codes often cannot be cloned and instead require true programming, where the car learns a brand-new key onto its system.
In plain English
Cloning is making a copy so identical the car thinks it is the original. You need a working key to copy from, and the copy then starts the car just like the first one.
It is great for a quick spare on the right vehicles. But not every car allows it, and you cannot clone if you have already lost the only key.
Cloning versus programming
Cloning duplicates an existing key's identity. Programming teaches the car a new, separate key. Cloning is usually quicker and does not change anything in the car, but it only works on systems that allow it and only when you have a key to copy. Programming works more broadly, including all-keys-lost, but takes more steps. A locksmith picks the right approach for your vehicle.
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