Meta tags define how browsers are to render web page content and they also provide information which search engines use to determine the relevance of the web page. The most commonly used meta tags are: charset, description, keywords, and author.
The charset defines how a web page is to be rendered by a web browser.
<meta name="description" content="Base64 - Learn about HTML meta tags">
The description is exactly this – a description of the webpage which is commonly used by search engines.
<meta name="keywords" content="Learn online, Learn HTML, Base64, Learn to code, HTML tutorial">
Keywords assist search engines in determining the relevance of a particular web page when compared to search terms.
<meta name="author" content="Base64">
This one doesn’t need explaining ?