RSS or Atom feeds are an alternative way of allowing visitors to keep up-to-date on your website. Essentially, the visitor subscribes to your feed through their e-mail software, browser, or other news readers, and then they get notified when you post new entries. This saves them from having to periodically revisit your website to see if there is new content or not. Having a feed available can make the difference between a visitor being someone who visited your website and liked it (but does not come back) and someone who visited your website and now reads every new post.
When building a feed, the easiest approach is to start with a pre-built ExpressionEngine feed template. This will take care of the top portion of the feed (containing meta-information such as the date, the URL of the entry, and so forth), meaning you only have to make a few customizations so that the feed displays the content from your custom fields.
An RSS 2.0 template can be found at http...