This is what a set of car keys looks like: 1 - ignition key; 2 - electronic training key of the immobilizer; 3 - electronic working keys of the immobilizer; 4 - key for door and trunk locks.
The ignition key flag has a key number on it, to keep the number secret, cut off and remove the flag.
The key number for the door and trunk locks is stamped on the key itself, so that the locks do not need to be changed in case of loss of keys; new keys can be ordered from the manufacturer using their numbers.
The red electronic key for the immobilizer is a training key, the two black electronic keys are working keys. The use of the immobilizer keys is described in more detail in Section 9 "Electrical Equipment" in the subsection "Car Anti-Theft System (ATS)".