Feed basics
Feeds are pure contents (or just summaries of content) presented in a structured way via XML, and are usually organized with the most recent information on top. You can always stay up-to-date using feed aggregators (software that can read feeds). Using them, you can also have the content you want delivered or collected for you in the way and place you want. This applies not only to written content from blogs or new websites, but also audio and video content (that is, podcasts).
Typically, web feeds are either in Really Simple Syndication (RSS)or Atom format. RSS has changed over the past decade, and thus is often referred by a version number. The most up-to-date version of RSS is RSS 2.0.1. The older versions that are still somewhat in use are 0.91 and 1.0. However, to be honest, in my some-years' experience with blogging and WordPress, I can't recall a moment when I had to worry about or even be aware of the version I'm currently using. This is one of those things that goes unnoticed...