A guide (on how to install a Notepad++ alternative for Linux) told me to type this command to the terminal:
sudo add-apt-repository ppa:notepadqq-team/notepadqq
What does this command do?
sudo runs the following command as an administrator.
add-apt-repository adds the following repository to the list of places the system goes to look for software.
ppa:notepadqq-team/notepadqq is the name of the repository where the notepadqq team upload updates to their software.
One you run this command, you will be able to install notepadqq by typing
sudo apt-get install notepadqq
and if you install it this way, the system update program will also find and install updates to notepadqq.
For future reference check the man pages or www.explainshell.com