The apt-get command is a command-line tool, which works 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.

# To search a package:
apt search package

# To show package informations:
apt show package

# To fetch package list:
apt update

# To download and install updates without installing new package:
apt upgrade

# To download and install the updates AND install new necessary packages:
apt dist-upgrade

# Full command:
apt update && apt dist-upgrade

# To install a new package(s):
apt install package(s)

# To uninstall package(s)
apt remove package(s)