[URLnf="http://www.amazon.com/complete-SEO-guide-beginners-ebook/dp/B00L76RXWE/ref=sr_1_16?ie=UTF8&qid=1403612611&sr=8-16&keywords=beginners+seo"]Here[/URLnf] is the link for the book on amazon.com
....and here is an excerpt on the meta description. I had to cut the example images etc in order to post here, so it may not be perfectly clear.
THE DESCRIPTION META TAG
What is the description Meta tag?
The description Meta tag appears in the header section of an HTML document. It is used to provide a brief summary of what the page is about. The contents of the description Meta tag are not visible on the actual page seen by the visitor. The contents of the description Meta tag are often, but not always used by search engine in the search engine results pages as a summary of the pages content. Occasionally, search engine may display a snippet of text from the actual page content, if it is deemed to be more relevant to the searchers query. Sometimes the pages description from The Open directory Project (DMOZ.org) may be used instead of the description Meta tag contents.
How the description Meta tag is used
A common misconception is that Google uses the description Meta tag as a factor when ranking a page. Trying to optimize the description Meta tag in order to improve the pages SEO is a wasted effort. The tag is still very important though, as it is often displayed in the search engine results pages, just under the title of the page. The description Meta tag can entice the searcher to click on your link and not any of the others on the results page. It is essentially a way to sell your page to the potential visitor.
The description Meta tag is a way for you to provide searchers with a brief and enticing summary of what the page is about. It is important to write the description Meta tag in a way that it will appeal to humans, not to search engines. Simply stuffing it full of keywords will not affect your pages ranking in any way, but doing so will irritate the human reader, and make them less likely to click through to your page.
Think of the description Meta tag as an advertisement for your page. Write it in such a way that people will want to click on it.
Search engines and the description Meta tag
Search engines frequently use the first 20 - 25 words of the description Meta tag as the summary of the page contents in the search engine results, but if your site is listed on the DMOZ (Open Directory Project), then the description from the directory may be used instead. You can prevent the search engines from using the description from the DMOZ. Depending on the search query, search engines may ignore both of the above descriptions and use a snippet of text from the actual web page in the search engine results instead.
Cropping the description Meta tag
As can be seen in the preceding description Meta tag, the contents have been cropped. This is indicated by the '...' at the end of the description. Ensure that you stick to the word limit in order to avoid cropping, and include the most important words at the beginning of the description. This way, if it is cropped, then you will still be getting your message across.
How to write the description Meta tag
Remember that the purpose of the description Meta tag is to act as a selling point for your page, and not as a way to try and rank higher in the search engine results. It should give the searcher a clear and concise indication of what your page is about, and must be written in such a way as to encourage searchers to click through to your page.
Keywords in the description Meta tag
Use a description tag that contains keywords that are relevant to the contents of the page, but do not stuff the description tag with keywords in an effort to try and influence the pages ranking in the search engines results pages, as it will not work. Search engines highlight the searchers search terms in the description when displaying the search results for the searchers query, so using keywords can draw attention to your listing, but the description should still be written in such a way that it would entice the searcher to click through to your page.
Should every page have a unique Meta description?
It would be nice for every page on a website to have a unique Meta description tag, but on large websites, this would simply take too much time to do. What is important is that no two pages should have the same Meta tag description tag. If your website is very large, then make sure to create unique Meta description tags for your home page and your top landing pages as well as any other important pages on your website.
Remember that Google does not use the content of the Meta description as a ranking factor, but it often includes the contents of the Meta description tag in the SERPs, so having a unique Meta description tag for your main pages is important. If Google cannot find a Meta description tag for a page, it will use a snippet of text from the content of that page. For pages that you do not have time to create unique Meta description tags for, it is better to leave the Meta description tag empty instead of duplicating Meta descriptions across multiple pages.