apt-get update updates all the packages?

Question

I am new to ubuntu and would like to know if apt-get update updates the list of installed as well as uninstalled but available packages from various repos?

Answer 1

apt-get update just updates the list of available packages from the repositories configured in /etc/apt/source.list and /etc/apt/source.list.d.

It does not update any installed software packages, that's the job of apt-get upgrade.

Answer 2

Yes, apt-get updates your full list of packages available in your added repo not just the ones that are installed.