sudo apt-get commands

From the Ubuntu documentation,

The apt-get command is a powerful command-line tool used to work with Ubuntu's Advanced Packaging Tool (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.

Update the Package Index - Run this command periodically to make sure your source list is up-to-date.

sudo apt-get update

Upgrade Packages - This command upgrades all installed packages.

sudo apt-get upgrade

Upgrade Packages with "smart upgrade" - The same as the above, except add the "smart upgrade" checkbox.

sudo apt-get dist-upgrade

Install a Package

sudo apt-get install <app name>

Remove a Package

sudo apt-get remove <app name>