SEO metadata is what appears on search engine result pages when a website comes up for certain queries. It includes the title of the page and its meta description (descriptive text below the title).
It's your title tag that's visible in the SERPs and when your content is shared on any other platform. On the other hand, the H1-tag is the displayed “title” on the actual page. Don't confuse this with the title that's visible in the tab of your browser - this is the title tag.
The meta description tag in HTML is the 160 character snippet used to summarize a web page's content. Search engines sometimes use these snippets in search results to let visitors know what a page is about before they click on it.
Meta titles should be short. It is best to keep them under 60 characters (spaces included). We recommend to describe what the page is about in the beginning of the title and add the name of a website or company at the end. Using keyword meta titles is a good way to give signals of relevancy to search engines. Only include keywords in the title if they are also included in the body content of the page. Only optimize a page with keywords for which it is relevant. Google relies heavily on the title of a page and its relevancy to the content on the page to determine its appropriate ranking.
The meta description is the text that appears below the title of the page on search engine result pages. This text can be entirely customized by the owner of a site, but Google reserves the ability to change it and use content from the page in the meta description if it judges the original description non-descriptive, inappropriate or irrelevant to the actual content of the page.
A meta description should not be longer than 160 characters, spaces included. It should describe what the page is about and include at least one keyword used in the corresponding title of the page.