From the Debian Reference 2.2.2 2002-11-30: "The internals of this Debian binary package format are described in the deb(5) manual page. Because this internal format is subject to change (between major releases of Debian), always use dpkg-deb(8) for manipulating .deb files."

From the dpkg-deb man page: "dpkg-deb packs, unpacks and provides information about Debian archives. .deb files can also be manipulated with ar and tar alone if necessary. Use dpkg to install and remove packages from your system."

You might find lots of example .deb files in directory '/var/cache/apt/archives/'. With 'dpkg-deb -I somepackage.deb' you might get a general overview of what this package offers in particular. 'dpkg-deb -c somepackage.deb' lists all files which will be installed.

List content of the .deb file with 'ar tv somepackage.deb'. Use the 'x' option to extract the files.