What is RSS?
RSS means Really Simple Syndication
RSS (Rich Site Summary) is a format for delivering regularly changing web content. Many news-related sites, weblogs and other online publishers syndicate their content as an RSS Feed to whoever wants it.

Why RSS? Benefits and Reasons for using RSS
RSS solves a problem for people who regularly use the web. It allows you to easily stay informed by retrieving the latest content from the sites you are interested in. You save time by not needing to visit each site individually. The number of sites offering RSS feeds is growing rapidly.

What do I need to do to read an RSS Feed?
Feed Reader or News Aggregator software allow you to grab the RSS feeds from various sites. You can find list of RSS readers here. Once you have your Feed Reader, it is a matter of finding sites that syndicate content and adding their RSS feed to the list of feeds your Feed Reader checks. Many sites display a small icon with the acronyms RSS, XML, or Atom.

What is 0-day?

0-day, pronounced ”Zero Day” or sometimes ”Oh Day”, means ”new.”

The term has it’s origins in the warez scene, but has become firmly entrenched in the exploit trading scene. If a game or an exploit was release on yesterday, it is 1-day. If it was released a full week ago, it is 7-day.
0-day is used to refer to exploits released today and exploits that have not yet been released.
An exploit might be 0-day to you because it was just publicly released, but two-months old to members of the group that coded the exploit