In DotNetNuke's "Page" management section there is a field called "Metatags" as shown below
If we click on "More settings" another screen pops up with a "Keywords" field.
Can some one tell me how the metatags different than keywords used in DNN?
Just two different ways to skin the same cat. DNN has multiple ways to get to the Page Settings, you are looking at the Page Management screen in the first screenshot, and the "Page Settings" screen in the second screenshot.
Keywords get put into the HTML for the page
example:
<meta id="MetaKeywords" name="KEYWORDS" content="CMS template, ASP .NET CMS, Web Builder, Evoq Content, Evoq Social, CMS Forums, Social Community Software,DotNetNuke,DNN" />
same thing with the Description
<meta id="MetaDescription" name="DESCRIPTION" content="Create modern websites using DNN Software's online content management system, which has been the backbone for over 750,000 websites worldwide" />
Why two different interfaces? Someone didn't like the way DNN did things by default, so they built the page management interface and gave them different labels for settings.