When sharing a page, some services use the shared URL to scrap some of the page HTML code for meta data. It is used for creating the preview image, title and description for shared links.

<meta property="og:title" content="Example Page"> <meta property="og:image" content="https://example.com/images/image.jpg"> <meta property="og:description" content="This is just an example page."> <meta property="og:url" content="https://example.com/page.html"> <meta name="twitter:card" content="summary_large_image">