Linux distributions: family tree

In short: Almost all distributions belong to a few families: Debian, Red Hat, Arch, SUSE and independents. Whoever knows one family understands the package manager and files of its descendants too.

In more detail: A distribution (distro) bundles kernel, tools, desktop, package manager and defaults. Descendants build on the parents’ packages.

In detail

• Debian family: Debian → Ubuntu → Linux Mint, Kubuntu, Xubuntu, Lubuntu, Pop!_OS, elementary OS, Zorin OS. Debian → Kali, Tails, MX Linux, Raspberry Pi OS, Devuan. Package format deb, tool apt.
• Red Hat family: Fedora → RHEL → Rocky Linux, AlmaLinux, CentOS Stream, Oracle Linux. Format rpm, tool dnf.
• Arch family: Arch → Manjaro, EndeavourOS, CachyOS, SteamOS (base), Garuda. Tool pacman.
• SUSE family: openSUSE (Leap, Tumbleweed) → SUSE Linux Enterprise. Tool zypper.
• Independent: Gentoo (source code, Portage), Slackware (the oldest still maintained), NixOS (Nix), Void (xbps), Alpine (apk), Clear Linux.
• Target groups: beginners (Ubuntu, Mint, Zorin), developers (Fedora, Pop!_OS), servers (Debian, Ubuntu LTS, Rocky), security (Kali, Tails, Qubes), games (SteamOS, Bazzite, Nobara), tinkerers (Arch, Gentoo, NixOS).
• Choosing: first clarify desktop and goal, then choose a distribution. Try distros with a live USB stick or in a virtual machine.

See also: Linux distributions, Package management on Linux at a glance