What are meta keywords?

On the web, a keyword is a reference to the content and/or the type of meta element included in a given web page's HTML code to aid in the page's indexing. A keyword meta element may include several comma-separated keywords (or keyword phrases, each of which may contain several individual words) as follows:

<meta name="keywords" content="keyword, another keyword, one more keyword" />

Looking back to the 90s, the search engine crawlers were relatively poor in terms of analysis capabilities, and, thus, the meta keywords were a simple way to detect the topics of a page. Historically, it has been the first way to optimize for search engines, however, no major search engine today claims to read the keywords which has raised the question of whether they are still needed at all.