Meta tags are HTML codes being put on the header of a website, following the title tag. They take multiple forms and serve various purposes. In the perspective of the search engine optimization when people refer to meta tags, they regularly refer to meta description tags and meta keywords tag.

The meta description tag and meta keywords tag are suggested so that webmasters could have a reliable system for providing meta document data to user agents, such as search engines. Unfortunately, so many dishonest webmasters are abusing the meta description and meta keywords tag that  leads search engines to degrade their website's worth,  or worse, penalize them.

In addition to the recognized meta description and the meta keywords tags, there are other valuable meta tags, as well as the meta http-quiv tag, meta refresh tag, the meta robots tag, the meta copyright tag, and the meta author tag,  and many others. These tags are used to teach user agents such as web browsers and search engine spider on the selection of topics.