What is ppa?
PPAs are for non standard software/updates. They are generally used by people who want the latest and greatest. If you are going extra lengths to get this kind of software, then you are expected to know what you are doing. The selection in the Software Centre is ample for most human beings.
ppa 是一种非标准非官方软件源，由社区人员提供。添加 ppa 可以安装最新版的软件或升级。这些新软件官方系统中不包括，如果不添加 ppa，需要等待官方升级才可以安装新软件。
添加 ppa 的命令：add-apt-repository
sudo add-apt-repository ppa:gwibber-daily/ppa