A lot goes into creating a successful eCommerce website. Obviously, the product needs to be in demand and you have to provide sufficient 
customer support. However, there are plenty of little things, too, that must be addressed if you hope to have people visit your website in the first place. This is known as SEO (search engine optimization) and one important feature is your meta tags.
Meta tags are just part of your webpage’s HTML code. Although your visitors can’t read them, they’ll be extremely attractive to search engines if you do them right and, in many ways, this is even more important. Generally, meta tags include a brief summary of what the page is about. You’re essentially using this to tell search engines what users will find there.
So obviously, it’s of the utmost importance to take these seriously. Many people who run sites don’t and some don’t even bother with them in the first place. Optimizing them, then, can mean crushing the competition.
First, it should go without saying that this copy needs keywords that are relevant to your site and/or this page. This is SEO 101.
The code itself includes the title, description, your relevant keywords and any robot tags. The most important of these are your title and description as they’re what your search engine will display when providing users with results.
Type your meta tags out like you normally would, from left to right. However, you also want to make sure your most important keywords are closer to the beginning of your copy. That’s because search engines read left to right and the sooner they find your keywords, the better.
Your title tag should be no more than 60 characters and no less than 10. Fewer than 10 words is giving up valuable real estate and after 60, you’re simply not getting any returns on your effort.
The meta tag for your page’s descriptions should stop at 200 characters. Again, though, don’t leave too much white space here. Although users will see this in their search engine results, 200 characters aren’t enough to make them bored. So swing for the fences in terms of keywords and description. Sell them on your site!
Writing out meta tags may not be as exciting as learning about different plugins, uploading videos or using SEO tricks to achieve higher rankings. However, it’s still one of the most important things you can do to get in the good graces of search engines and it’s an extremely easy tactic to master.
Source:
http://www.siteground.com/tutorials/sem/meta_tag_optimization.htm