Ubuntu PPA (Personal Package Archives) provides additional software for ubuntu.

To install a PPA, use command add-apt-repository.

For example, to install latest proprietary graphics drivers on ubuntu, we need to enable graphics-drivers PPA. To enable, run

sudo add-apt-repository ppa:graphics-drivers/ppa -y

Now update apt cache by running

apt-get update

When you add a PPA, apt source file for the PPA is created at

root@hon-pc-01:~# ll /etc/apt/sources.list.d/  | grep graphics
-rw-r--r-- 1 root root  219 Feb 24 01:48 graphics-drivers-ppa-trusty.list
-rw-r--r-- 1 root root  219 Feb 24 01:48 graphics-drivers-ppa-trusty.list.save
root@hon-pc-01:~# cat  /etc/apt/sources.list.d/graphics-drivers-ppa-trusty.list
deb http://ppa.launchpad.net/graphics-drivers/ppa/ubuntu trusty main
# deb-src http://ppa.launchpad.net/graphics-drivers/ppa/ubuntu trusty main
# deb-src http://ppa.launchpad.net/graphics-drivers/ppa/ubuntu trusty main
root@hon-pc-01:~# 

Removing a PPA

You can remove software installed from a PPA safely by running command

ppa-purge PPA-NAME

For removing gaphics drivers PPA, run

sudo ppa-purge graphics-drivers