What is the function of "noIndex, follow" attributes in Metatags?

[Venu]

I know noindex, nofollow don't display website in the Google Search results.
Google bot not "index" the content in the database.
Google bot index the webpage, but not not give positive rating to the webpages.
but another commend "noindex, follow", how is this possible?
Without indexing the content, how to give positive rating to the webpage?
Please explain depth of the "noindex, follow" attributes?
Without indexing a webpage how to give link juice?
It means crawling and indexing both are different.?
It means after crawling give link juice without indexing (display on the Search results) a website?

[Venugopal]

noindex, follow means .it will not index but it will give the link juice to website or page..

hope you understand

[Chris]

no index means that the search engine will crawl you site but will not index it and will not save it in the database so when you will search it the query in the search engine so the page will not be displayed in the search engine.

No follow means you don't want you site reputation to be followed to that site as you don't think it is a reputed site and will lower your reputation.