This package contains a major mode for editing APT’s “.list” files.

The “/etc/apt/sources.list” file and other files in
“/etc/apt/sources.list.d” tell APT, found on Debian-based systems and
others, where to find packages for installation.

This format specifies a package source with a single line, e.g.:

    deb http://deb.debian.org/debian stable main contrib

For more information about the format you can read the manual
pages “apt(8)” and “sources.list(5)”, also on the web at URL
‘https://manpages.debian.org/stable/apt/sources.list.5.en.html’
and URL ‘https://manpages.debian.org/stable/apt/apt.8.en.html’.