Core, Extra, Multilib? Unraveling the Arch Linux Repositories
Quoting: Core, Extra, Multilib? Understand Arch Linux Repositories —
I hope this article helped you get familiar with the arch repos. The gist of this article is that if you want to install Steam or Wine in Arch Linux, you have to enable the multilib repo.
I will advise you to stay away from all the testing repos if you don't know what you are doing. It is not worth the hassle to install the latest kernel or the flashy new KDE version from testing repos.
I am telling you from my experience that sometimes Pacman refuses to revert back to stable packages, which gets pretty frustrating. However, a VM will come in handy if you just want to get rid of the itch to experience and test the latest/greatest software packages.