<meta name="description" content="description here">
<meta name="keywords" content="Keywords separated by comma's">
<meta name="author" content="your name">
This is really not all that hard to understand on the first tag <meta name="description" content= PLACE A STRONG DESCPRPTION OF YOUR SITE HERE"> make it clear and decisive so you attract the proper kind of traffic.
in the second meta tag <mete name="keywords" content=" PLACE YOUR KEYWORDS HERE">
in the second area place your keywords for your site. Use Google Adword |"keyword tool" to find the most suitable ones. avoid the ones with high competition you will usually never win with them to many big sites compete for them. use the ones with 800-1200 searches a month and the highest CPC ( cost per click) that you can find relating you your site. don't use more then 20.
in the third meta <mete name="author" content=" YOUR NAME"> place your name it simply shows your the one who created this page.
I strongly advise placing meta tags in your web page. Doing this is not a requirement but it will bost your traffic.