A brief summary description of fewer than 160 characters in the search engine result of the contents of a page and why someone would want to visit it.
This snippet describes the page content for the benefit of users and search engines. If not composed by the website . This is often displayed on search engine results pages below the page title as a sample of the content on the page. If not composed by the website owner, the search engine will compose it from the first lines of text on the page. This is critical for search engines to understand page contents as well as giving users an idea of the information they will find after clicking the link.
It's also one of the meta tags that gives a description of the page in 160 characters. The meta description is an important aspect of a webpage because it is what appears in Google searches and other search engine results.