It's not the having a package manager that makes it specific, it's that it's ports-like. It's also a great feature that I'm a huge fan of.
It doesn't do nearly as much patching as other distros (save for Slackware or CRUX) to packages making reporting bugs upstream much more straightforward.
This explains it better than I do: https://wiki.archlinux.org/index.php/The_Arch_Way
