RSS = Really Simple Syndication

When a visitor subscribes to your RSS Feed you have created, they receive updates to your website via their personalized aggregator without having to check your website over and over and over again.

A subscriber can get several feeds from different websites and receive the latest updates from all of them in one place--or an "aggregator."

Subscribers "pull" information from your website (photo galleries, blogs, news, podcasts and/or vidcasts) to themselves unlike E-newsletters, that "push" information.

Aggregators allow subscribers listen on demand via computer, ipod, mobile phone or other device.

Some RSS Feeds can also be added directly to your website to enhance it. Examples include, weather, news tickers, etc. Local example.

Many websites such as eventful and YouTube have built in RSS capability:

Feedburner