When website publish updates frequently such as news sites or blogs, how could visitors track new updates on that website?, they have to periodically visit the website to see if there exist any updates, this is not a systematic approach and not also convenient. In our busy world, many times you will forget and miss vital information that is important to you.
As an alternative, you can subscribe to website newsletter, but many sites have no newsletter and even if it has, you have to wait until they send the email, and even it will not say everything in their email. In many other cases we do not want to disclose our emails because of our fear from the increasing spam.
Nowadays there is a concept of site feed that is designed to solve this problem, the site owner put all new items in an xml file format and publish the feed URL. The feed URL should be technically correlated with the website content, may be all the content are in database so that web pages and site feeds are generated on the fly, or maybe the data is originally XML and on the fly converted to html for web viewers.
Technically there are two standards for the feeds, Atom and RSS, we will not discuss them in this article, but I already hyberlinked them for more details.
On Web pages that offer feeds, web feeds (RSS or Atom) are typically linked with the word “Subscribe”, an orange square, 
, or a rectangle with the letters 
or 
.
How to read such feeds? Special piece of software called Newsreaders (or Aggregators) can scan these feeds, automatically letting you know when the sites have been updated and bring updates to you automatically. You can schedule such tools to check every 10 minutes or every day morning or whatever you like. Some tools are web based and others are desktop based.
As example, Thunderbird is a feed reader- beside its email reading capabilities-, Google Reader is an example of web based reader. Actually there exist more than 67 application and service, atomenabled.org has a good directory of all tools and services at http://www.atomenabled.org/everyone/atomenabled/index.php?c=5
There exist many developer tools to assist in creating feeds, atomenabled.org have a nice list at http://www.atomenabled.org/everyone/atomenabled/index.php?c=7 that have many tools with Java, php, and .Net.
As Web Feed is the standard of getting updates and is widespread, all websites should be feed enabled, this is not an option, millions of users already use feed-reader and aggregators services/applications to track website changes especially news sites.
Of course you can read our blog feed through http://ahm507.blogspot.com/atom.xml, and you can also subscribe by email if this is still easier to you.