If the meta robots tag has a value of “no index, no follow” what does it mean? Does Google uses keyword tags?

The meta robots tags is used to instruct search engine spiders how to index your site and to either scan the page for links or not to.
For example your tag [“no index, no follow” ] tells a search spider not to index/look at the page and that the rest of the site should not be indexed/looked at either.
You can find more info about metatags here: http://www.metatags.org/meta_name_robots
Google doesn't use the keywords meta tag in web ranking but they do have some other products that might make use of the data. Keywords were a lot more important about fifteen to seventeen years ago before it was abused so much that it eventually came all but meaningless for that purpose. Meta robot tags are actually a separate issue and apply no only to the ones that you might first think of (Google, Yahoo, Bing) but also apply to places that archive.org that are actually indexing the entire Internet.
Don't misunderstand this to mean that your robots tags 'have' to be used. There are many products and spider that completely ignore your robots tags and index your site anyhow. It's not going to keep you safe from the FBI or the Department of Homeland Security (for instance).
Search engines doesn't use the search phrases meta tag in web position but they do have some other items that might create use of the information. Keywords were a lot more essential about 15 to 17 decades ago before it was misused so much that it gradually came all but useless for that objective.
Last edited by Abran; 04-26-2014 at 02:12 AM.
According to my point of view, the meta robot tag is a way to determine how to page follow the indexing strategy and it provides the information to the user in search result. You can also say in other word that it is a page specific strategy which is used for the index controlling purpose.
If we talk about the "no follow, no index", means you are not approaching any kind of indexing for your page.
Yes, Google uses the Keword tags, the reason is that Google wants to provide the best information to the user.
anything "robots" related will instruct website crawlers from search engines like google with whatever instruction they are.
no index for example will tell them not to add the page to their results index, so they wont be added to the search engines.
no follow tags, affect the ranking of the site that the link leads to. for example, links in signatures. if you post on a site with a url in your signature, and the link has "no follow" added to it by the site holding the link, then google will add them to a list of links to that url that have "no follow" attached to them, if there is no tag, they will go in a different list.
follow links (without the "no follow" tag) have the strongest affect on search results.
BUT, having ONLY followed links looks suspiscious to google, and will be detrimental.