Being a simple command-line tool, has numerous advantages over other package management tools available in Ubuntu for server administrators.This page describes how to handle the packages on your system using apt-get and related commands.
However, there are occasional changes made in the Foundation's Raspbian image that require manual intervention, for example a newly introduced package.
These packages are updated infrequently and after extensive testing.
(APT) performing such functions as installation of new software packages, upgrade of existing software packages, updating of the package list index, and even upgrading the entire Ubuntu system.
These are not installed with an upgrade, as this command only updates the packages you already have installed.
The kernel and firmware are installed as a Debian package, and so will also get updates when using the procedure above.