The Wikipedia article Linux distribution describes and compares popular Linux distributions.

Ubuntu is described as "Ubuntu focuses on usability... The Ubiquity installer allows installing Ubuntu to the hard disk from within the Live CD environment without the need for restarting the computer prior to installation. Ubuntu also emphasizes accessibility and internationalization, to reach as many people as possible...
The most recent version of Ubuntu comes installed with a wide range of software including an older version of the OpenOffice.org productivity suite, the internet browser Firefox, the instant messenger Pidgin (formerly known as Gaim), the BitTorrent client Transmission, and the raster graphics editor GIMP."