A command line utility to add and remove APT software repositories, such as PPAs. It is part of the software-properties-common package and installed in Ubuntu by default.
add-apt-repository is a python script that can be used to control APT software repositories via command line. It is generally used to add external sources such as PPAs (ppa-purge can be used to remove such sources more gracefully)
The script can append repositories to the /etc/apt/sources.list file or create a new file in the /etc/apt/sources.list.d directory. It requires root privilege.
Common usage example:
sudo apt-add-repository ppa:atareao/telegram
This creates a file, for example /etc/apt/sources.list.d/atareao-ubuntu-telegram-yakkety.list. After adding the repository, update APT:
sudo apt update
And packages from the added repository are now available and can be installed with APT:
sudo apt install telegram