What is Other (Applications) in PS4 System Memory?

I've had storage space issues for some time. Since my PS4 is of the opinion today that it won't download the new Modern Warfare update, I wanted to see what I can delete (I have 3 applications). Since none of these applications come into question, I found the culprit named "Other" in the system memory, which you can't select and can't delete the corresponding one. My question is, what is it and how can you delete it?

If you delete applications, you can download them again at any time, the saved data will NOT be lost. (No matter whether CD or not, I accidentally deleted something and everything was still there with both variants).

Delete unnecessary pictures from the gallery. You could also install a hard drive or connect it via USB. See if you have any other applications that you may be able to delete.

I tried everything you said, because that's actually what is recommended everywhere. As I said I only have 3 applications. I just want to know what "other" means.

I assume something like backgrounds, additional files.