Note that the platform uses different icons for regular and predefined catalog items (see fig. 3.73).
Despite the fact that users can edit the code or description for both items, they cannot edit the predefined item names that you specify in Designer. Later you will use these names to call the predefined items from 1C:Enterprise script.
So, the configuration algorithms can be based on predefined items.
Now you can see the main difference between regular and predefined catalog items from the configuration point of view.
Regular items are not permanent. Users can create and delete them. Although the configuration can distinguish them from each other, you cannot use them in the algorithms because they can disappear at any time.
Predefined items are permanent. They are always available, regardless of user actions.
In theory, users can delete predefined items but we will not give them rights for interactive deletion of predefined objects (or interactive deletion of any objects at all, see Lesson 22. Users and their roles).
Therefore, the configuration algorithms can rely on predefined items. This is why each predefined item has a unique name, so that it can be referenced using 1C:Enterprise script.