What is a Noindex Meta Tag?

Noindex is a meta tag that instructs search engines not to include a specific page in their search results.
The noindex tag can be placed in the section of the page’s HTML or in an HTML header returned by the web server.
If a page has been indexed by Google and then a noindex tag was added, the page will be removed from Google search results after Google crawls the page again.
Example:

<meta name='robots' content='noindex, follow' />
Noindex Meta Tag in view-source.

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