Displaying RSS items from an external feed
RSS is a technology that has been around since the early days of the internet. Its main purpose is to allow users to be easily notified when new content is published on their favorite sites. The underlying mechanism behind RSS feeds is a simple XML file that contains the site's headlines along with updated timestamps and part or all of the content of new items that are posted. Applications or services called RSS aggregators (for example, Feedly and NewsBlur) can monitor the content of RSS feeds and display new items as they are published or notify users of this new content. It is interesting to note that podcasts use the same RSS feed technology to publish their episodes online.
While RSS is not as popular as it used to be, most news-based websites still publish RSS feeds. WordPress includes a copy of the SimplePie library to allow developers to easily fetch and cache RSS feed data and easily display it on a site.