I'd say Arch is for people who have the time to learn and care how most parts of the OS work. I use it because I like to heavily customize everything, and want complete control over how everything is done.

Take a look at the beginners guide to get a feel: https://wiki.archlinux.org/index.php/Beginners%27_guide

Manjaro is an easier to use spin off from Arch. Has a graphical package manager and installer.

http://manjaro.org/

The name Manjaro reminds me of "One guy, one jar". :/