As funny as the name may sound, NOOBS (New Out of Box Software) is actually designed to get newbies comfortable with their first-time exploits of the wonderful little Pi. The Raspberry Pi Foundation released NOOBS to ease the installation of one of four most popular operating systems for the Pi out there.
We recommend that first-time Pi users start by downloading and installing our New Out of Box Software (NOOBS) onto a 4GB (or larger) SD card.
NOOBS is available for download on the Pi’s official downloads page, along with a quick start guide that includes a graphical illustration of all of Pi’s components, terminologies, and instructions to install an operating system on the board with minimum fuss. The guide has been updated to accomodate for NOOBS.
On first boot, NOOBS presents you with a choice of operating systems to install, including Raspbian, Pidora, and two flavours of XBMC. Raspbian is a Debian-based Linux distro specifically designed for Raspberry Pi, with the largest software repository of around 35,000 packages. Pidora is a similar distro derived from Fedora.
Once you have installed an operating system, you can return to the NOOBS interface by holding down shift during boot; this allows you to switch to a different operating system, or overwrite a corrupted card with a fresh install of the current one.