A meta-tag is an HTML tag that gives information about the content of a web page, such as what HTML specifications a web page follows or description of a web page's content. A meta-tag, however, does not affect how a web page is displayed on a browser. For online marketing, the most common uses for meta-tags are the keyword, description, and robots exclusion attributes. In fact, only some major search engines use meta-tag content for relevancy.
Some search engines use meta-tag content when they display the results of a search query.
When writing meta-tag content, spend more time writing a good description than writing a keyword list. In terms of online marketing, the description is more important than the keywords list. Using singular and plural words in meta-tags We have personally found that people tend to type in the plural version of a word more than they type in the singular version of a word in search engine queries. For that reason, we tend to emphasize the plural version of a word in the meta-tags. When you analyze your site statistics to see which variations of your keywords and keyword phrases people are using to find your website, optimize your web pages for most commonly used keywords.