Debian packages are standard Unixar archives that include two tar archives optionally compressed with gzip (zlib), Bzip2, lzma, or xz (lzma2): one archive holds the control information and another contains the program data.
Debian packages can be converted into other packages and vice versa using alien, and created from source code using CheckInstall or Debian Package Maker.
Some core Debian packages are available as udebs (“micro debs”), and are typically used only for bootstrapping a Debian installation. Although these files use the udeb filename extension, they adhere to the same structure specification as ordinary deb files. However, unlike their deb counterparts, udeb packages contain only essential functional files. In particular, documentation files are normally omitted. udeb packages are not installable on a standard Debian system, but are used in Debian-Installer.