It is a card that comes with many security cylinders and is used to order copies of that key. Without the card, they cannot be duplicated.
The idea is simple: if the key cannot be copied just anywhere, you control how many there are. Someone who borrows a key for a while cannot have a copy made behind your back.
Keep it somewhere safe, out of sight and away from the keys. Do not leave it in the summer house or in the hall drawer. If you lose it, ordering copies becomes complicated.
We do not cut copies of keys. What we do is fit security cylinders with protected keys, which are very useful in rented homes or in houses that stay shut for months. It is all in security cylinders.