When you drop a link in Telegram and a pretty image and title appear — that's Open Graph.
Main tags
<meta property="og:title" ...> <meta property="og:description" ...> <meta property="og:image" content="https://site.uz/og.jpg"> <meta property="og:url" ...>
Image size
1200×630px — universal. JPG 100-200 KB.
Twitter Cards
For Twitter add twitter:card meta tags.