.deb

Install/uninstall .deb files

These files are Debian packages. The package files associated with Ubuntu have the .deb suffix because of Ubuntu's close relations with the Debian GNU/Linux distribution. You will need administrative privileges to install a .deb file (see the section called “Root And Sudo”).

1. To install a .deb file, simply double click on it, and then select Install Package

2. Alternatively, you can also install a .deb file by opening a terminal and typing:

sudo dpkg -i package_file.deb

3. To uninstall a .deb file, deselect it in your package manager, or type:

sudo dpkg -r package_name

source: verbatim from https://help.ubuntu.com/ubuntu/desktopguide/C/install-file.html