No-www is an initiative to make all websites accessible from both the http://www.example.com/ and http://example.com/ forms of their names.
The reason behind it is to standardize domain names providing web content and to avoid extraneous typing. Technically, domain names, including third level domains, are not meant to identify the type of content provided, but rather a host, which may provide different types of content. That is not a problem, since the content type is requested using the corresponding protocol. In the case of web pages, that is the HyperText Transfer Protocol (“http://”). You can read more about No-www on the official site and on Wikipedia.
P.S. computerhovel.com ;))