Meta tags are HTML elements that provide additional information about a web page to search engines, browsers, and other web services. They are placed within the head section of an HTML document and do not affect the visible content of the page. Meta tags help search engines understand the content, improve search engine optimization (SEO), and provide supplementary information to browsers and web crawlers. Here are some commonly used meta tags: 1. Title Tag: The title tag is one of the most important meta tags. It defines the title of the web page and appears as the clickable link in search engine results. It should accurately describe the content of the page and ideally contain relevant keywords for SEO. 

<title>Your Page Title</title>
2. Meta Description: The meta description tag provides a brief summary of the page's content. It often appears below the title in search engine results. While not a direct ranking factor, a well-written meta description can influence click-through rates. It should be concise, informative, and compelling. 

<meta name="description" content="Description of your page">
3. Meta Keywords (deprecated): In the past, the meta keywords tag was used to specify relevant keywords for search engines. However, search engines now largely ignore this tag due to misuse and keyword stuffing. It is no longer recommended to use this tag for SEO purposes. 

<meta name="keywords" content="keyword1, keyword2, keyword3">
4. Viewport Meta Tag: The viewport meta tag controls the layout and scaling of a web page on mobile devices. It ensures that the page is rendered appropriately across different screen sizes. It is crucial for creating responsive designs. 

<meta name="viewport" content="width=device-width, initial-scale=1.0">
5. Charset Meta Tag: The charset meta tag specifies the character encoding used by the web page. It helps browsers interpret and display the text correctly. UTF-8 is commonly used as it supports a wide range of characters. 

<meta charset="UTF-8">
6. Open Graph Meta Tags: Open Graph meta tags are used to provide structured data about a webpage when sharing it on social media platforms like Facebook, Twitter, and LinkedIn. These tags control how the page's title, description, image, and other elements appear in social media posts. 

<meta property="og:title" content="Your Page Title">
<meta property="og:description" content="Description of your page">
<meta property="og:image" content="URL of the image">
<meta property="og:url" content="URL of the page">
These are just a few examples of meta tags, but there are many more available for specific purposes like specifying robots instructions, setting the language, controlling cache behavior, and more. The usage and importance of meta tags may vary depending on the specific requirements of the web page and the intended audience.