Keywords is a list of comma-separated targeted phrases or words that relate to the content of the page. The description is a free-form paragraph/sentence style "overview" of the content on the page.
You must make sure that both of these are correct and makes sense... Use words or phrases which you are targetting as keywords.. and must make sure that those are present in ur site atleast 3 or 4 times...... Description is a brief idea about the site or page..... so write something desciptive at the sametime short with some keywords in it.......