Mastering these basic apt commands will elevate your CLI skills
As you may know, APT (Advanced Package Tool) is a command-line utility for managing packages on Ubuntu, Debian and derivative systems. Among others, it’s the tool you use to upgrade the system, add a repository, check if a package is available in a repo or install a package.
For Ubuntu and derivative systems, also dpkg and snap package managers are available, but in this article I will only cover APT.
1. APT Commands For Beginners: Update the Package List
sudo apt update
Technically speaking, this command does not update any package on the system. It only checks all the available repositories and updates the list. If there is a new version of Chromium available, after you run apt update, you will be able to install the new version on your system with apt install.

2. APT Commands for Beginners: Upgrade Installed Packages
sudo apt update
sudo apt upgrade
The apt update command updates the repository files and discovers the available software updates, while the apt upgrade commands upgrade does the actual upgrade of the packages.
3. APT Commands for Beginners: Install a Package
sudo apt update
sudo apt install <package-name>
It is a common practice to update the repository index with apt update, before installing anything new with apt install.
The apt install command installs the latest version of the package found inside the added repositories.
For example, to install GIMP, you can do sudo apt install gimp.

4. Mastering Apt: Remove a Package
sudo apt remove <package-name>
This removes a package, but keeps the current configuration files.
For example, sudo apt remove gimp removes GIMP.

5. APT Commands For Beginners: Purge a Package (Remove Configuration Files)
sudo apt purge <package-name>
This removes both the package and the configuration files. For example sudo apt purge gimp removes GIMP and all the customizations and saved configs.
This can also be used ever of gimp has been already removed with apt remove, deleting only the configuration files, if the software is not installed.

6. Mastering APT: Search for a Package
apt search <package-name>
This command looks inside the available repositories and shows if any package with or containing that name is available. No sudo is needed here, as this does not change any system file. For example, apt search mixxx shows the Mixxx version which is available via the already existent repositories.

7. APT Commands For Beginners: Show Package Information
sudo apt update
apt show <package-name>
It is common practice to refresh the repository index before using apt show, so that you see the information about the latest version of the package available. This is what apt show mixxx command outputs:

8. APT Commands For Beginners: List Upgradable Packages
sudo apt update
apt list --upgradable
This lists all the packages that have updates available.

9. APT Commands For Beginners: Clean Up Unused Packages
sudo apt autoremove
The sudo apt remove commands uninstalls all the packages that are not used anymore, because they were installed as dependencies for other packages.

10. APT Commands For Beginners: Fix Broken Install
sudo apt --fix-broken install
This command resolves and installs any missing or broken dependencies. Also, it offers to remove the dependencies which are not used anymore, similar to sudo apt autoremove.

By mastering these 10 commands you will be able to use the apt package manager efficiently on your Ubuntu, Linux Mint or another derivative system.