Arch Linux is an open source, rolling release Linux distribution. Arch Linux is kept up-to-date by regularly updating the individual pieces of software that it comprises. Arch Linux is intentionally minimal, and is meant to be configured by the user during installation so they may add only what they require.
Arch Linux provides monthly "snapshots" which are used as installation media.
Pacman, a package manager written specifically for Arch Linux, is used to install, remove and update software packages. Additionally, the Arch User Repository (AUR), which is the community-driven repository for Arch Linux provides packages not included in the official repositories and alternative versions of packages; AUR packages can be downloaded and built manually, or installed through an AUR 'helper'.
Arch Linux has comprehensive documentation in the form of a community-run wiki known as the ArchWiki.