Raspbian is the recommended operating system for normal use on a Raspberry Pi.
Raspbian is a free operating system based on Debian, optimised for the Raspberry Pi hardware. Raspbian comes with over 35,000 packages: precompiled software bundled in a nice format for easy installation on your Raspberry Pi.
Raspbian is a community project under active development, with an emphasis on improving the stability and performance of as many Debian packages as possible.