RSS Channels can be built for the contents of container Items. RSS Channels are web feeds which are used to publish frequently updated content such as Blogs, news items etc.
A RSS Channel typically contains a summary of all of the descending Items within the container Item, each with a link to the Item in the application. They are read by a RSS feed reader or an aggregator. An RSS Channel can be output in a number of different formats (0.91, 1.0 and 2.0) on a number of different schedules (manually, daily, weekly, monthly). Once a channel has been created for a Item, an orange "XML" icon will appear on the page. This is a link through to the RSS Channel which can be sent to interested parties who wish to subscribe to the feed.
Please read the following article for more information on RSS and its different formats: What is RSS?