An HTML tag used by Web page authors to provide a description for search engine listings.
The META description tag belongs in the <head> section of a Web page (above the <body> section), typically below the title tag and above the META keywords tag.
Writing good description tags is an important part of optimizing a site to rank well in the search engines and entice people to click on the listing. Search engines typically display 150 characters from the description tag, give or take a few dozen.
Descriptions should include very specific, keyword-rich writing. Do not use any keyword excessively, as search engines may perceive this as spamming. If possible, specific terms should be used early in the description to help search engines and visitors identify the main subject of the page, and also to avoid getting left out of the visible area.
see also: SEO Tools