Such pages typically describe the entity that owns the site, and may include self-promotional information, which AboutUs.com does not restrict. In many other cases the content of an entry consists of the whois data for the website.
Most entries were created by a web robot (bot); web searches by users direct the bot to create a page for a web domain. In many cases the content is simply a republication of the contents of the "About us", "About me", or similar page on the website.