Different classes of Linux packages

I do know that there are 4 different classes of packages in Linux: 1. Packages provided by the operating system 2. Packages provided by third parties 3. Self-made packages of third-party software 4. Self-made packages of your own software I am trying to find examples for each of these classes so I can better understand it. So I came up with the following: 1. packges like firewalld or kernel packages 2. packages like virtual box or vmware player 3. Am no sure about this one, maybe a developer developing a package that's related to or built on another 3rd party software?? Tmux custom versions ?? maybe 4. this one is just easy Am I right in these examples, I would need just a little bit more elaboration here on #3. Self-made packages of third-party software, do you guys have any examples. Thank you