Rss

RSS is nothing more than a simple data format used to syndicate (redistribute) content that is updated frequently to subscribers to a website.

The format allows you to distribute content without the user navigates.Any user can subscribe and get the latest news delivered to your aggregator or RSS reader, which will alert you when there is new information to read.

So the user can obtain current information on your website easily, simply and without registration. More information about this system on Wikipedia.