RSS (an acronym for 'Really Simple Syndication') is an XML-based file format for providing well-defined syndicated content to "feed readers." Stack Exchange sites provide RSS feeds of content available on many of its pages. For example:

- [`/feeds`](/feeds) Recent Questions
- [`/feeds/user/ID`](/feeds/user/1) User Activity
- [`/feeds/featured`](/feeds/featured) Featured Questions
- [`/feeds/tag/TAG`](/feeds/tag/discussion) Tagged Questions
- [`/feeds/question/ID`](/feeds/question/1) A Particular Question

See also *[What other hidden or inobvious RSS feeds are available on Stack Exchange and its sites?](https://meta.stackexchange.com/q/151519)* for an elaboration on the different kinds of RSS URLs.