What Is the Meta Description Tag?
It’s a snippet of HTML code that belongs inside the section of a web page. It is usually placed after the Title tag and before the Meta keywords tag (if you use one), although the order is not important.
The proper syntax for this HTML tag is:

If you’re using a content management system (CMS), look for a field to fill out that’s called Meta Description, or possibly just “Description.”

There are 3 important ways that Meta descriptions are being used today that make them an important part of your SEO and overall online marketing strategy:
1. They can be used as the description (or part of the description) of your page if it shows up in the search results.
2. They are often used as part of the descriptive information for your pages when Google shows “extended sitelinks” for your site.
3. They are often used as the default description in social media marketing links such as Facebook and Google+.
Let’s look at each of these in more detail.

1. Meta Descriptions in the Search Results
People often think that whatever they put in their Meta description tag will be the default description that the search engines use under the clickable link to their site in the search results. While this is sometimes true, it’s not always the case.
Currently, if you’re searching for a site by its URL (for example www.h2lonlinemarketing.co.za) Google tends to use the first 20 to 25 words of your Meta description as the default description in the search engine result pages (SERP). However, if you have a listing at DMOZ, also known as the Open Directory Project (ODP) and are not using the “noodp” tag, they may default to that description instead. (Do a search at Google for www.amazon.com to see an example.)
Bing and Yahoo!, on the other hand, don’t always default to the Meta description tag for URL searches. Sometimes they do, and sometimes they don’t. A search for www.h2lonlinemarketing.co.za   at Bing or Yahoo! shows content from my home page as the description rather than the contents of our Meta description tag.
Of course, real people aren’t typically searching for a site by URL, so what the search engines show for those types of search queries is not as important as a true keyword search. So don’t get hung up on what you see when you search for your site by its URL or if you’re doing a “site:command” search to see how they’re indexing your pages.
Instead, go to your favorite web analytics program and find the keyword phrases that are currently bringing you the most traffic. Then see what your description looks like at Google when you type in those keywords.
And surprise! What you’ll find is that your search results description will be different for every search query! You may see any combination of the following used:
* Your entire Meta description tag text as the complete description (typically if it’s highly relevant and contains no more than 25 words).
* A full sentence pulled from your Meta description tag, but not the entire Meta description (if it contains more than one sentence).
* Text from one part of your Meta description mashed together with text from another part of it (if it’s more than 25 words long).
* Some text from your Meta description mashed together with some text from the page.
* Some text from your page mashed together from some other text from your page (nothing from the Meta description).

Some of the circumstances that cause Google to not use text from your Meta description may include:
* The information in the Meta description tag was not specific to the page it was on.
* The search query used some words that were not in the Meta description, but those words (or some of them) were used in the page content.

My recommendation is to always use keywords on any pages where you get search engine visitors (or hope to get them). Make them very specific to the page they’re on by describing what someone will find when they click through to the page from the search results, while also using variations of your targeted keywords.
Because Google will show only show around 20 to 25 words as your description, many SEOs recommend that you limit this tag to a certain number of characters.

For instance, if you’re optimizing a page for 3 different keyword phrases, you could write a 3-sentence Meta description tag, with each sentence focusing on a different phrase. You could probably even insert more than 3 phrases in those sentences if you’re a good wordsmith. The idea, however, is not to stuff this tag full of keywords, but to write each sentence to be a compelling marketing statement – a statement that naturally uses the keywords people might be typing into Google to find your site.

Overall, the Meta description tag gives you a little bit more control over what people might see before they click over to your site. The more compelling it is, the more clickthroughs you should see. If your Meta description tags can help with that, then it’s certainly worth the few minutes of time it takes to create interesting, keyword-rich tags that sum up what users will find when they arrive!