The AUR (Arch User Repository) is a collaborative set of build-scripts for a ton of software not covered by Parabola or Arch'es software repos. It contains some non-free software-- but don't worry, we don't recommend any of that to you. ;)
To install an AUR program, just
tar -xvf the file,
cd into the new directory, and run:
$ sudo makepkg -si
(Argument s means that it'll install dependencies automatically, and i means it'll install when complete.)
With that, the program builds, and will install when complete. See, AUR isn't that hard! Cheers.