Meta tags are a main factor in SEO.This targets only crawlers. Human visitors can’t see meta tags unless view source of the HTML. There are different types of html meta tags.

Most important meta tags are

Keyword meta tag – Use less than 10 words .All the word in this tag MUST appear somewhere in the body text in the html page.If not, it can be penalized for irrelevance.One word should not repeat more than twice. If not, it is considered as spam. Most of webmasters think this was deprecated. But there are instance that this works well for some search engines. Best practice is to put most important words in the content should be put in keyword tag. Keyword meta tag can be several words separated by comma . Better to keep short and meaningful words that are in the page.

Description meta tag –This contains a small description about the page. Most search engines put this in SERP. Less than 200 characters are preferable,Google no longer rely on this tag. But most of webmasters use this tag.