When appending items from a different blend file,
Check the Fake User option to automatically set a Fake User to the items.
This means that appended items that are not used within the file will not be deleted when closing it.
It’s useful for times when you append a whole library of materials or other assets into a file, so that you don’t have to make use off all of them before saving and closing, and they will still be available in the file the next time you load it.
In other words, you wont need to append the assets again the next time if you didn’t make use of them..