META data are HTML codes that can be added in the heading of the website's page, following a title tag. Relative to web optimization, when they mention META data, they're usually talking about the META description label as well as the META key phrases or keywords. The META data in your website have an effect on the way in which many SE like Google trace and spot website pages. You should have at least a minimum of three META Tags that you need to utilize in order to be sure that your webpage is optimized.

META data in search engines are used for several means:

1) To let Google and other search engines know what your website is all about. Some search engines like Google is going to take the first few lines of your website page to function as the brief explanation of your website in case you don't set an Meta description for that page. This description is a lot more important than you think it seems.

2) Meta robots tag are used for tracking purposes as most search engines also are looking for it as one factor of one's website. For instance, if search engines like Google couldn't find this type of tag, they are going to think that it could be listed and be placed behind links on a webpage. If you'd like to take action and rank on Google or other SE, you should make use of a META tag to identify it.

3) META data are utilized to evaluate which keywords and phrases your page will likely be shown in. So for your page to be classified in these search engines once the user looks for a certain term, these keywords or key phrases needs to be in your META Keywords. I am not sure though if nowadays, these internet SE continually employs this tag. There's no harm in putting 3-5 Meta keywords on your source code, anyway.

There are other Meta information that SE identify and consider. On the other hand, the tags that I have discussed here are the most popular tags that relate to the majority of SE.