RSS provides a way for web sites to distribute their content outside of a web browser. A news web site might have an RSS newsfeed which contains breaking stories, while a magazine web site may provide a feed with excerpts of their latest articles. Here you can see my diary entries when I'm 'out and about'

An actual RSS file is nothing more than a list of items, each of which has a title, a description and maybe a link to the web page where the item appears.