You can read more about its features at
http://www.ubuntu.com/products/whatisubuntu/1004features.
There are also the variants, including Kubuntu, the Netbook Remix and Ubuntu Studio. I am currently trying them out in virtual machines on my Ubuntu 9.04 PC and am considering installing Ubuntu Studio 10.04 as my main OS, as I want more features for things like audio and video editing and creation.
http://ubuntustudio.org/