[thejdude]

"What makes distributions different are mainly the package manager and the packages in the repositories."

...and the packaging/updating philosophy, the packaging/defaults, the configurability. How they handle your hardware (hotplugging printers, monitors, mice). Batteries included or not. Power management.

E.g. Fedora always uses the latest upstream packages and doesn't patch them very much. Debian/Ubuntu/Mint use stable packages and patch them heavily. Many years ago one such patch in the (stable) Ubuntu kernel broke my (officially supported) file system, causing data loss. OTOH, Fedora can be a bit harsh to use for newbies.