How do Video Preview Links work

Troubleshooting
4

Here is an example, on this video https://www.youtube.com/watch?v=ih2xubMaZWI

        <meta property="og:site_name" content="YouTube">
      <meta property="og:url" content="https://www.youtube.com/watch?v=ih2xubMaZWI">
    <meta property="og:title" content="OMFG - Hello">
    <meta property="og:image" content="https://i.ytimg.com/vi/ih2xubMaZWI/maxresdefault.jpg">

      <meta property="og:description" content="&#39;Feeling Sheepish&#39;...http://bit.ly/SuicideSheepSpotify MERRY CHRISTMAS!!!! Download... https://bitly.com/alexomfghello OMFG https://soundcloud.com/alexomfg h...">

    <meta property="al:ios:app_store_id" content="544007664">
    <meta property="al:ios:app_name" content="YouTube">
      <meta property="al:ios:url" content="vnd.youtube://www.youtube.com/watch?v=ih2xubMaZWI&amp;feature=applinks">

      <meta property="al:android:url" content="vnd.youtube://www.youtube.com/watch?v=ih2xubMaZWI&amp;feature=applinks">
    <meta property="al:android:app_name" content="YouTube">
    <meta property="al:android:package" content="com.google.android.youtube">
    <meta property="al:web:url" content="https://www.youtube.com/watch?v=ih2xubMaZWI&amp;feature=applinks">

    <meta property="og:type" content="video">
        <meta property="og:video:url" content="https://www.youtube.com/embed/ih2xubMaZWI">
        <meta property="og:video:secure_url" content="https://www.youtube.com/embed/ih2xubMaZWI">
        <meta property="og:video:type" content="text/html">
        <meta property="og:video:width" content="1280">
        <meta property="og:video:height" content="720">
        <meta property="og:video:url" content="http://www.youtube.com/v/ih2xubMaZWI?version=3&amp;autohide=1">
        <meta property="og:video:secure_url" content="https://www.youtube.com/v/ih2xubMaZWI?version=3&amp;autohide=1">
        <meta property="og:video:type" content="application/x-shockwave-flash">
        <meta property="og:video:width" content="1280">
        <meta property="og:video:height" content="720">

        <meta property="og:video:tag" content="MrSuicideSheep">
        <meta property="og:video:tag" content="OMFG Hello">
        <meta property="og:video:tag" content="OMFG">
        <meta property="og:video:tag" content="Electro House (Musical Genre)">
        <meta property="og:video:tag" content="Electro">
        <meta property="og:video:tag" content="8bit Music">
        <meta property="og:video:tag" content="Chiptune (Musical Genre)">
        <meta property="og:video:tag" content="Bass">
        <meta property="og:video:tag" content="Electronic">

    <meta property="fb:app_id" content="87741124305">

        <meta name="twitter:card" content="player">
    <meta name="twitter:site" content="@youtube">
    <meta name="twitter:url" content="https://www.youtube.com/watch?v=ih2xubMaZWI">
    <meta name="twitter:title" content="OMFG - Hello">
    <meta name="twitter:description" content="&#39;Feeling Sheepish&#39;...http://bit.ly/SuicideSheepSpotify MERRY CHRISTMAS!!!! Download... https://bitly.com/alexomfghello OMFG https://soundcloud.com/alexomfg h...">
    <meta name="twitter:image" content="https://i.ytimg.com/vi/ih2xubMaZWI/maxresdefault.jpg">
    <meta name="twitter:app:name:iphone" content="YouTube">
    <meta name="twitter:app:id:iphone" content="544007664">
    <meta name="twitter:app:name:ipad" content="YouTube">
    <meta name="twitter:app:id:ipad" content="544007664">
      <meta name="twitter:app:url:iphone" content="vnd.youtube://www.youtube.com/watch?v=ih2xubMaZWI&amp;feature=applinks">
      <meta name="twitter:app:url:ipad" content="vnd.youtube://www.youtube.com/watch?v=ih2xubMaZWI&amp;feature=applinks">
    <meta name="twitter:app:name:googleplay" content="YouTube">
    <meta name="twitter:app:id:googleplay" content="com.google.android.youtube">
    <meta name="twitter:app:url:googleplay" content="https://www.youtube.com/watch?v=ih2xubMaZWI">
      <meta name="twitter:player" content="https://www.youtube.com/embed/ih2xubMaZWI">
      <meta name="twitter:player:width" content="1280">
      <meta name="twitter:player:height" content="720">

You can see og:site_name, og:title, og:url, etc…

For sites, those are the information used to provide the information on mattermost, when u post a link to some post or news from some site.