In SEO , Meta tags keywords and Meta tags description is very important as they tell the Search Engines that what is all about your site is . A meta keywords tags are the groups of important words of your site .Meta description tags is the brief explanation of summary about your site.
So from SEO point of view they are most important for any site.
There is a very simple code for putting them.
Here it is
meta content='DESCRIPTION HERE' name='description'
meta content='KEYWORDS HERE' name='keywords'
meta content='AUTHOR NAME HERE' name='author'
DESCRIPTION :Write your blog/site description
KEYWORDS:Write the keywords of your blog/site
AUTHOR NAME:Write the author's name(Your name)