Fedora
Red Hat's community distro — bleeding edge for later RHEL versions. Fedora Workstation, Server, CoreOS, Silverblue (immutable). 6-month releases.
Founded 2003 after the Red Hat Linux ⇒ RHEL split. DNF package manager (since F22), RPM packages. Default GNOME desktop. Drives many new Linux technologies (systemd, Wayland, PipeWire). Linus Torvalds + Lennart Poettering (systemd creator) use Fedora. Fedora Atomic / Silverblue is the immutable OS frontier — the base swaps atomically.