A RSS feed is a list of articles on your site that someone who uses a RSS feedreader can follow the updates on your site.
•RSS (most commonly expanded as "Really Simple Syndication") is a family of web feed formats used to publish frequently updated works—such as blog entries, news headlines, audio, and video—in a standardized format. ...
A site map (note the spelling) is a page on your website or blog that shows all the major sections of your site. It is used by your visitors to find things on your site. Search engine bots can find this too and follow the links to pages within your site.
A Sitemap (note the spelling) is an XML file with a list of pages on your site that certain search engine bots use to find pages on your site. A search engine bot must understand the Sitemaps protocol
to read this file.