“Arch Linux is a rolling release system. What this means is that
you do not get releases at specific intervals in time, like you do
with Ubuntu, OpenSuse or Fedora. Instead there is a constant stream
of updates that are uploaded on the distribution servers and that
you can pull almost everyday. These updates are uploaded after a
testing period by the Arch Linux testing community (you can switch
to the testing mirrors if you wish) and it is up to you to choose
if you want to install them or not.
Such a rolling release process eliminates the need to accomplish
major upgrade and makes you gain time, as you typically end up
installing your Arch Linux system once, or twice if you really
screwed up something.