What is Meta Tags?
Meta elements are HTML or XHTML elements used to provide structured metadata about a Web page. Such elements must be placed as tags in the head section of an HTML or XHTML document. Meta elements can be used to specify page description, keywords and any other metadata not provided through the other head elements and attributes.

Meta elements provide information about a given webpage, most often to help search engines categorize them correctly. They are inserted into the HTML document, but are often not directly visible to a user visiting the site.

Examples:
1. Not Correct
meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"

2. This is Correct
meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"
meta name="author" content="Boyan Kostadinov (www.indexhelp.se)"
meta name="description" content="Index HELP is free URL database. The database is design to ensure that your URL become visible and popular on the net. IH is the middle of several other databases pointing to different web sites."
meta name="keywords" content="Free Search Engine Optimization Help, Index Help, Page Rank, DB1, DB2, DB3, Check Page Rank, www.indexhelp.se, Search Engine Optimization, Free Search Engine Help "


Bonus:
meta name="robots" content="index,follow" - Allows all robots to visit all files
meta name="verify-v1" content="+x52Ldyi4wvsaTd/238fcvsrnqeG1h96bKxGr/X0o=" - Google Webmaster Tools