Google explains the "Robots Exclusion Protocol"
Several webmasters and web search engine optimizers were confused by Google's Robots Exclusion Protocol. The latter is the standard for controlling how web pages on a particular site are indexed. Simplier said, it talks about noindex, nofollow, noarchive and nosnippet meta tags.
Earlier, Google released a detailed explanation and examples of how mechanisms work to control access and indexing of websites. The Google Blog has a basic but clear explanation of the robots exclusion protocol.
In a nutshell:
NOINDEX tag tells Google not to index a specific page
NOFOLLOW tag tells Google not to follow the links on a specific page
NOARCHIVE tag tells Google not to store a cached copy of your page
NOSNIPPET tag tells Google not to show a snippet aka description under your Google listing, it will also not show a cached link in the search results
For an in-depth discussion about Robots Exclusion Protocol, click here.
