The tags placed in the <head> element to provide meta information about the document are called meta-tags.
Meta tags are tags placed in the
<head> element to provide meta information about the document being served. They are not supposed to be directly seen by page visitor; they help browsers to properly display the page, and search engines to index it.
Important part of the family are
<meta http-equiv="..."> tags, that provide equivalents for HTTP Headers when it's impossible to send HTTP headers due to server's configuration.
Other common attributes are keywords, description, language and robots.