tl;dr Why do some .deb's install programs while other's don't, and what does apt-get update return in the console/why does it always seem to "get" bionic security repositories?
I am a very new linux user, and I am a bit confused on how some packages work. I also am seeing conflicting info on apt-get update.
1) I am trying to install NordVPN. I can follow the instructions easy enough, which is listed here. https://nordvpn.com/download/linux/
Why does the initial .deb file you download not actually install NordVPN. What's the difference between that and a .deb file for Steam? What is nordvpn-release.deb actually doing? Are some debs just packages referencing repositories of other debs?
2) As I understand it, apt-get update is supposed to update a repository of packages, and apt-get upgrade is supposed to act on that updated repository.
But if that's the case, how come running apt-get update twice returns two different logs? It seems to be installing something afterall. When I install the nordvpn-release.deb, and use apt-get update, I first get a three "Gets" related to NordVPN packages. BUt when I run it again, two of those disappear and the last one turns into HITS. Shouldn't it just return the same thing, because it's just getting me a list of up to date packages? Why are consecutive uses of apt-get update returning different things? And why does update always seem to "Get" Bionic-security?