Transponder key programming is based on a chip integrated into the car key. This chip was inserted to provide additional security to the car. When this chip was installed on a key a message was sent to the engine that this key is matched. In case of transponder not respond or not programmed specifically the engine Of the car not get proper message and car will not start.
It is not necessary that a transponder key program hand to hand but in many cases keys can be made Somewhere else and then bring to the locksmith for installing transponder programming. Auto locksmith can also remove existing transponder keys from the car's computer so that only New key will work.