The purpose of the meta element is to provide meta-information about the document.
Meta tags are used to supply information for search engines that will not be seen by the
web surfer unless they were to view your web site's HTML.
A D V E R T I S E M E N T
In the past, meta tags were a primary way for the site to be recognized by web spiders,
but the internet community abused the meta tags to artificially increase their ranking
in the search engine databases.
Keywords for Search Engines
To index your pages some search engines on the WWW will use the name and content
attributes of the meta tag.
This meta element defines a description of your page:
<meta name="description" content="Free Web tutorials on HTML, CSS, XML, and XHTML">
The intention of the name and content attributes is to describe the content of a page.
However, some search engines have stopped using them entirely,
since too many webmasters have used meta tags for spamming,
like repeating keywords to give pages a higher ranking.
Unknown Meta Attributes
Sometimes you will see meta attributes that are unknown to you like this:
<meta name="security" content="low" >
Then you just have to accept that this is something unique to the site or to the author of the site,
and that it has probably no relevance to you.