See image for a one-look explanation:
As the image shows, I'm missing the 'cardboard box' icons from the Software Updater. I know that they are supposed to be their from another machine that runs 18.04, but on this machine with the same OS, the icons are missing.
See this image to illustrate the missing icon:
So now my question to you: What causes this? Is it important? How can I fix this?